This Registration Statement on Form 10 is being filed by Arizona Public Service Company (“APS”), a wholly-owned subsidiary of Pinnacle West Capital Corporation (“Pinnacle West”). Certain information required in this Form 10 is incorporated by reference from the Pinnacle West/APS Annual Report on Form 10-K for the fiscal year ended December 31, 2005 filed on March 13, 2006 (the “2005 Form 10-K”). The 2005 Form 10-K is a combined report filed by two separate registrants: Pinnacle West and APS. The information required with respect to each of Pinnacle West and APS is set forth within the applicable items in the 2005 Form 10-K. Only the applicable information relating to APS from the 2005 Form 10-K is incorporated into this Form 10.

     Incorporated herein by reference from “Item 1. Business” in the 2005 Form 10-K.

     Incorporated herein by reference from “Item 1A. Risk Factors” in the 2005 Form 10-K.

     Incorporated herein by reference from “Item 6. Selected Financial Data,” “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and “Item 7A. Quantitative and Qualitative Disclosures about Market Risk” in the 2005 Form 10-K.

     Incorporated herein by reference from “Item 2. Properties” in the 2005 Form 10-K.

     Omitted.

     Omitted

     Omitted

     Omitted

     Incorporated herein by reference from “Item 3. Legal Proceedings” in the 2005 Form 10-K.

     Incorporated herein by reference from “Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchase of Equity Securities” in the 2005 Form 10-K.

     In March 2005, APS caused the issuance of $163,975,000 aggregate principal amount of the Maricopa County, Arizona Pollution Control Corporation Pollution Control Revenue Refunding Bonds (Arizona Public Service Company Palo Verde Project) 2005 Series A-Series E in a tax-exempt financing under Title XIII of the tax reform act of 1986 and Section 103 of the internal revenue code of 1954 for the purpose of refunding pollution control bonds previously issued. The underwriters for the new bonds were UBS Financial Services Inc., JP Morgan Securities Inc., Citigroup Global Markets Inc., Goldman, Sachs & Co. and Banc of America Securities LLC. The underwriters were paid an underwriting fee of .45% of the principal amount of the bonds purchased by the underwriters and UBS Financial Services Inc. also received a management fee of .075% of the principal amount of the bonds. In March 2004, APS caused the issuance of $166,150,000 aggregate principal amount of the Navajo County, Arizona Pollution Control Corporation Pollution Control Revenue Refunding Bonds (Arizona Public Service Company) 2004 Series A- Series E and $12,850,000 aggregate principal amount of the Coconino County, Arizona Pollution Control Corporation Pollution Control Revenue Refunding Bonds (Arizona Public Service Company) 2004 Series A in a tax-exempt financing under Title XIII of the tax reform act of 1986 and Section 103 of the internal revenue code of 1954 for the purpose of refunding pollution control bonds previously issued. The underwriters for the new Navajo bonds were Goldman, Sachs & Co., Banc One Capital Markets, Inc., UBS Financial Services Inc., Morgan Stanley & Co. Incorporated, and Banc of America Securities LLC, and Goldman, Sachs & Co. acted as underwriter for the new Coconino bonds. The underwriters were paid an underwriting fee of .45% of the principal amount of the bonds purchased by the underwriters, and Goldman, Sachs & Co. also received a management fee of .05% of the principal amount of the bonds. In addition, from time to time, outstanding pollution control bonds issued on behalf of APS in similar tax-exempt financings are remarketed by independent remarketing agents as a result of optional or mandatory tenders by the holders of such bonds or by independent broker-dealers in auctions for such bonds in an auction-rate mode. The sales of such bonds are exempt under Section 3(a)(2) of the Securities Act of 1933.

     The general terms and provisions of our common stock are summarized below. This summary does not purport to be complete and is subject to, and is qualified in its entirety by express reference to, the provisions of our articles of incorporation. As of the date of this Form 10, all of our outstanding common stock is held by Pinnacle West and we have no preferred stock outstanding. However, subject to certain limitations, our Board of Directors has the authority, without any further action by our shareholders, to issue from time to time shares of preferred stock, in one or more series and to fix the designations, preferences, rights, qualifications, limitations and restrictions thereof.

     Under our articles of incorporation, we have the authority to issue 100,000,000 shares of common stock, par value $2.50 per share.

     Subject to any preferential rights of any series of preferred stock, holders of shares of common stock will be entitled to receive dividends on the stock out of assets legally available for distribution when, as and if authorized and declared by our Board of Directors. The payment of dividends on the common stock will be a business decision to be made by our Board of Directors from time to time based upon results of our operations and our financial condition and any other factors as our Board of Directors considers relevant. Payment of dividends on the common stock may be restricted by loan agreements, indentures and other transactions entered into by us from time to time. An Arizona Corporation Commission (“ACC”) financing order requires APS to indefinitely maintain a common equity ratio of at least 40% and does not allow APS to pay common dividends if the payment would reduce its common equity below that threshold. As defined in the ACC financing order approving the arrangement, common equity ratio is common equity divided by common equity plus long-term debt, including current maturities of long-term debt. At December 31, 2005, APS’ common stock equity ratio, as defined, was approximately 54%.

     Except as specified below, holders of common stock and preferred stock are entitled to one vote for each share held of record. Arizona law provides for cumulative voting for the election of directors. If six or more quarterly dividends accrued thereon shall not have been paid with respect to any outstanding preferred stock, the holders of such preferred stock will have the right to elect the lesser of six directors or one-fourth of the total number of members of the board of directors at the time, in addition to their other voting rights. The preferred stock will also have special voting rights in matters involving the preferences or privileges of the preferred stock and certain extraordinary corporate occurrences.

     Subject to any preferential rights of any series of preferred stock, holders of shares of common stock are entitled to share ratably in our assets legally available for distribution to our shareholders in the event of our liquidation, dissolution or winding up.

     The holders of common stock have no pre-emptive rights to subscribe for other shares except with respect to an offering of additional common stock, or securities convertible into common stock, for money, other than by (a) a public offering of all such shares, (b) an offering of all of such shares to or through underwriters or investment

bankers who shall have agreed promptly to make a public offering of such shares, or (c) an offering of all such shares to our stockholders, our employees or our customers.

     Outstanding shares of our common stock are fully paid and not liable to further calls or assessment by us.

     The Arizona Business Corporation Act (the “ABCA”) permits extensive indemnification of present and former directors, officers, employees or agents of an Arizona corporation, whether or not authority for such indemnification is contained in the indemnifying corporation’s articles of incorporation or bylaws. Specific authority for indemnification of present and former directors and officers to the fullest extent permitted by applicable law is contained in Section 7.01 of APS’ Bylaws. Such indemnification is mandatory. Article Fifth of the APS Articles of Incorporation permits indemnification of current and former directors and officers if the board determines in good faith that the person did not act, fail to act or refuse to act willfully or with gross negligence or with fraudulent or criminal intent.

     Under the ABCA, in order for a corporation to indemnify a director or officer, a majority of the corporation’s disinterested directors, special legal counsel, or the shareholders must find that the conduct of the individual to be indemnified was in good faith and that the individual reasonably believed that the conduct was in the corporation’s best interests (in the case of conduct in an “official capacity” with the corporation) or that the conduct was at least not opposed to the corporation’s best interests (in all other cases). In the case of any criminal proceeding, the finding must be to the effect that the individual had no reasonable cause to believe the conduct was unlawful. Indemnification is permitted with respect to expenses, judgments, fines and amounts paid in settlement by such individuals, except that, in the case of a proceeding by or in the right of the corporation, indemnification is limited to reasonable expenses incurred in connection with the proceeding. However, a corporation cannot indemnify a director in the cases noted in clause (ii) of the second sentence of the following paragraph. Broader indemnification is allowed, with certain limitations, for a director as provided in a corporation’s articles of incorporation, and for an officer who is not also a director or where the basis on which the officer was made a party to the proceeding is an act or omission solely as an officer, as provided in the articles of incorporation, bylaws, a resolution of the board of directors or a contract.

     Indemnification under the ABCA is permissive, except in the event of a successful defense, in which case a director or officer must be indemnified against reasonable expenses, including attorneys’ fees, incurred in connection with the proceeding. In addition, the ABCA requires Arizona corporations to indemnify any “outside director” (a director who is not an officer, employee or holder of more than five percent of any class of the corporation’s stock or the stock of any affiliate of the corporation) against liability unless (i) the corporation’s articles of incorporation limit such indemnification, (ii) the director is adjudged liable in a proceeding by or in the right of the corporation or in any other proceeding charging improper financial benefit to the director, whether or not involving action in the director’s official capacity, in which the director was adjudged liable on the basis that financial benefit was improperly received by the director, or (iii) a court determines, before payment to the outside director, that the director failed to meet the standards of conduct described in the preceding paragraph. With certain limitations, a court may also order that an individual be indemnified if the court finds that the individual is fairly and reasonably entitled to indemnification in light of all of the relevant circumstances, whether or not the individual has met the standards of conduct in this and the preceding paragraph or was adjudged liable as described above.

     In addition, we have, from time to time, entered into and/or may enter into agreements to indemnify certain of our directors and officers to the fullest extent allowed by law, subject to certain exceptions. To the extent the Board or shareholders may in the future wish to limit or repeal our ability to provide indemnification to our officers and directors, such repeal or limitation may not be effective as to directors or officers who are parties to any indemnification agreements because their rights to full protection would be contractually assured by such agreements.

     In Arizona, a corporation may purchase and maintain insurance on behalf of a director or officer of the corporation against liability asserted against or incurred by the individual arising from the individual’s status as a director or officer. We maintain insurance on a regular basis (and not specifically in connection with this offering) against liabilities arising on the part of directors and officers out of their performance in such capacities or arising on the part of APS out of the foregoing indemnification provisions, subject to certain exclusions and to the policy limits.

     Incorporated herein by reference from “Item 8. Financial Statements and Supplementary Data” in the 2005 Form 10-K.

     None.

Financial Statements and Financial Statement Schedule

     Incorporated herein by reference from “Item 8. Financial Statements and Supplementary Data — Index to Financial Statements and Financial Statement Schedule” in the 2005 Form 10-K.

     The documents listed below are being filed or have previously been filed on behalf of APS and are incorporated herein by reference from the documents indicated and made a part hereof. Exhibits not identified as previously filed are filed herewith.

     Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized.