<PAGE>


                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549


                                  FORM 10-Q/A

             (X)  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
                    OF THE SECURITIES EXCHANGE ACT OF 1934
                 For the quarterly period ended June 30, 1999


             ( )  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
                    OF THE SECURITIES EXCHANGE ACT OF 1934
                  For the transition period from ____ to ____

                        Commission file number 333-79587


                       CALIFORNIA STEEL INDUSTRIES, INC.
             (Exact name of registrant as specified in its charter)


           DELAWARE                                                  33-0051150
(State or other jurisdiction of                                (I.R.S. Employer
incorporation or organization)                              Identification No.)


       14000 San Bernardino Avenue
          Fontana, California                                             92335
(Address of principal executive offices)                             (Zip Code)


Registrant's telephone number, including area code:  (909) 350-6200



Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.  (  )  Yes  (X)  No


As of August 5, 1999, 1,000 shares of the Company's common stock, no par value,
were outstanding.

<PAGE>


                               Explanatory Note
                               ----------------

     This Form 10-Q/A is being filed to include statements of comprehensive
income for the three months and six months ended June 30, 1999 in Item 1 of the
Company's Form 10-Q for the Quarter Ended June 30, 1990.

                       CALIFORNIA STEEL INDUSTRIES, INC.

                               Table of Contents
<TABLE>
<CAPTION>
                                                                                        Page
                                                                                        ----
Part I.  Financial Information

         Item 1.  Financial Statements

<S>                                                                                     <C>
            Consolidated Condensed Balance Sheets as of
              June 30, 1999 and December 31, 1998......................................   2

            Consolidated Condensed Statements of Income for three months ended
              June 30, 1999 and 1998...................................................   3

            Consolidated Condensed Statements of Income for six months ended
              June 30, 1999 and 1998...................................................   4

            Consolidated Condensed Statements of Comprehensive Income for the
              three months ended June 30, 1999.........................................   5

            Consolidated Condensed Statements of Comprehensive Income for the
              six months ended June 30, 1999...........................................   6

            Consolidated Condensed Statements of Cash Flows for the six months
             ended June 30, 1999 and June 30, 1998.....................................   7

            Notes to Consolidated Condensed Financial Statements.......................   8
</TABLE>

<PAGE>


                         PART I.  FINANCIAL INFORMATION

ITEM 1.  FINANCIAL STATEMENTS

                       CALIFORNIA STEEL INDUSTRIES, INC.
                                AND SUBSIDIARY
                     Consolidated Condensed Balance Sheets
                   (In thousands, except per share amounts)

<TABLE>
<CAPTION>
                                                                              As of                As of
                                                                             June 30,           December 31,
                               Assets                                          1999                1998
                                                                        ------------------   -------------------
                                                                            Unaudited
<S>                                                                     <C>                  <C>
Current assets:
     Cash and cash equivalents.......................................             $ 10,807             $ 11,962
     Trade accounts receivable, less allowance for doubtful
      receivables of $1,080,000 and $720,000 in 1999 and 1998........               61,181               53,630
     Inventories.....................................................              155,386              173,396
     Deferred income taxes...........................................                4,545                4,545
     Other receivables and prepaid expenses..........................                4,554                5,211
                                                                                  --------             --------
            Total current assets.....................................              236,473              248,744
                                                                                  --------             --------
Investment in affiliated company.....................................               22,350               34,726
Other assets.........................................................                4,758                   --
Property, plant and equipment, net...................................              257,696              251,163
                                                                                  --------             --------
            Total assets.............................................             $521,277             $534,633
                                                                                  ========             ========
                   Liabilities and Stockholders' equity
Current liabilities:
     Notes payable to banks..........................................             $     --             $103,700
     Current installments of long-term debt..........................                   --               20,000
     Accounts payable................................................               52,261               50,550
     Income tax payable..............................................                9,234                   --
     Other accrued expenses..........................................               18,628               22,344
                                                                                  --------             --------
            Total current liabilities................................               80,123              196,594
                                                                                  --------             --------
Long-term debt, excluding current installments.......................              220,000              120,000
Deferred income taxes................................................               26,740               26,740
Stockholders' equity:
     Class C preferred stock, $10,000 par value per share.
      Authorized 3,000 shares; issued and outstanding 3,000 shares...               30,000               30,000
     Common stock, no par value.  Authorized 2,000 shares; issued
      and outstanding 1,000 shares...................................               10,000               10,000
     Retained earnings...............................................              163,453              151,299
     Accumulated other comprehensive income..........................               (9,039)                  --
                                                                                  --------             --------
            Total stockholders' equity...............................              194,414              191,299
     Commitments and contingencies...................................                   --                   --
                                                                                  --------             --------
            Total liabilities and stockholders' equity...............             $521,277             $534,633
                                                                                  ========             ========
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       2

<PAGE>

                 CALIFORNIA STEEL INDUSTRIES, INC.
                           AND SUBSIDIARY
            Consolidated Condensed Statements of Income
                    (Unaudited) (In thousands)

<TABLE>
<CAPTION>
                                                                                Three Months Ended June 30,
                                                                       ---------------------------------------------
                                                                                1999                    1998
                                                                       -----------------------   -------------------
<S>                                                                    <C>                       <C>
Net sales...........................................................            $170,264              $180,559
Cost of sales, net of LIFO reserve..................................             135,770               158,703
                                                                                --------              --------
            Gross profit............................................              34,494                21,856
Selling, general and administrative expenses........................               7,762                 7,313
                                                                                --------              --------
            Income from operations..................................              26,732                14,543
Other income (expense):
     Equity in income (loss) of affiliate...........................              (3,337)                1,042
     Interest expense, net..........................................              (4,312)               (4,418)
     Other, net.....................................................                 652                   207
                                                                                --------              --------
            Income before income taxes..............................              19,735                11,374
Income taxes........................................................               8,099                 4,669
                                                                                --------              --------
            Net income..............................................            $ 11,636              $  6,705
                                                                                ========              ========
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       3
<PAGE>

                 CALIFORNIA STEEL INDUSTRIES, INC.
                           AND SUBSIDIARY
            Consolidated Condensed Statements of Income
                    (Unaudited) (In thousands)

<TABLE>
<CAPTION>
                                                                                 Six Months Ended June 30,
                                                                       ---------------------------------------------
                                                                                1999                    1998
                                                                       -----------------------   -------------------
<S>                                                                    <C>                       <C>
Net sales...........................................................           $331,258              $356,734
Cost of sales, net of LIFO reserve..................................            270,213               313,363
                                                                               --------              --------
            Gross profit............................................             61,045                43,371
Selling, general and administrative expenses........................             15,083                14,592
                                                                               --------              --------
            Income from operations..................................             45,962                28,779
Other income (expense):
     Equity in income (loss) of affiliate...........................             (3,337)                1,406
     Interest expense, net..........................................             (8,086)               (8,345)
     Other, net.....................................................                713                   189
                                                                               --------              --------
            Income before income taxes..............................             35,252                22,029
Income taxes........................................................             14,468                 9,043
                                                                               --------              --------
            Net income..............................................           $ 20,784              $ 12,986
                                                                               ========              ========
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       4
<PAGE>


                      CALIFORNIA STEEL INDUSTRIES, INC.
                              AND SUBSIDIARY
          Consolidated Condensed Statements of Comprehensive Income
                         (Unaudited) (In thousands)

<TABLE>
<CAPTION>
                                               Three Months Ended June 30,
                                               --------------------------
                                                 1999             1998
                                               --------         ---------
<S>                                            <C>              <C>
Net income...................................  $ 11,636         $ 6,705


Other comprehensive income:
   Foreign currency transition adjustments...    (9,039)            -
                                               --------         -------
Comprehensive income.........................  $  2,597         $ 6,705
                                               ========         =======
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       5
<PAGE>

                        CALIFORNIA STEEL INDUSTRIES, INC.
                                AND SUBSIDIARY
           Consolidated Condensed Statements of Comprehensive Income
                          (Unaudited) (In thousands)


<TABLE>
<CAPTION>
                                                    Six Months Ended June 30,
                                                    -------------------------
                                                      1999             1998
                                                    --------         --------
<S>                                                  <C>               <C>
Net income.....................................     $ 20,784         $ 12,986
                                                    --------         --------

Other comprehensive income:
  Foreign currency translation adjustments.....       (9,039)            -
                                                    --------         --------

Comprehensive income...........................     $ 11,745         $ 12,986
                                                    ========         ========
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       6
<PAGE>


                       CALIFORNIA STEEL INDUSTRIES, INC.
                                AND SUBSIDIARY
               Consolidated Condensed Statements of Cash Flows
                          (Unaudited) (In thousands)

<TABLE>
<CAPTION>
                                                                                 Six Months Ended June 30,
                                                                       ---------------------------------------------
                                                                                1999                    1998
                                                                       -----------------------   -------------------
<S>                                                                    <C>                       <C>
Cash flows from operating activities:
     Net income.....................................................           $  20,784              $ 12,986
     Adjustments to reconcile net income to net cash provided by
      operating activities
        Depreciation and amortization...............................              12,285                14,101
        Loss (Gain) on disposition and write-down of idle plant and
         equipment..................................................                 (11)                  282
        Undistributed (earnings) losses of affiliate................               3,337                (1,316)
        Dividends received from affiliate...........................                  --                   558
        Change in assets and liabilities:
          Trade accounts receivable, net............................              (7,551)              (10,472)
          Inventories...............................................              18,010               (19,564)
          Other receivables and prepaid expenses....................                 657                (3,192)
          Other assets..............................................              (4,758)                   --
          Accounts payable..........................................               1,711                 1,830
          Income taxes payable......................................               9,234                 5,443
          Other accrued expenses....................................              (3,716)                5,330
                                                                               ---------              --------
          Net cash provided by operating activities.................              49,982                 5,986
                                                                               ---------              --------

Cash flows from investing activities:
     Additions to property, plant and equipment.....................             (18,827)              (26,583)
     Proceeds from sale of property, plant and equipment............
                                                                                      20                    25
                                                                               ---------              --------
          Net cash used in investing activities.....................             (18,807)              (26,558)
                                                                               ---------              --------
Cash flows from financing activities:
     Net repayments under line-of-credit agreement with banks.......            (103,700)               17,682
     Repayment of notes payable to banks............................            (140,000)                   --
     Proceeds from issuance of long-term debt.......................             220,000                 5,000
     Dividends paid.................................................              (8,630)               (8,385)
                                                                               ---------              --------
        Net cash (used in) provided by financing activities.........
                                                                                 (32,330)               14,297
                                                                               ---------              --------
        Net decrease in cash and cash equivalents...................              (1,155)               (6,275)
     Cash and cash equivalents at beginning of period...............              11,962                10,343
                                                                               ---------              --------
     Cash and cash equivalents at end of period.....................           $  10,807              $  4,068
                                                                               =========              ========
Supplemental disclosures of cash flow information:
     Cash paid during the period for:
        Interest (net of amount capitalized)........................           $   6,079              $  8,221
        Income taxes................................................               5,235                 3,600
                                                                               =========              ========
</TABLE>

See accompanying notes to consolidated condensed financial statements.

                                       7
<PAGE>


CALIFORNIA STEEL INDUSTRIES, INC.
AND SUBSIDIARY
Notes To Consolidated Condensed Financial Statements

1.   Basis of Presentation
     ---------------------

     The accompanying unaudited consolidated condensed financial statements of
California Steel Industries, Inc. and its subsidiary as of and for the three and
six months ended June 30, 1999 and 1998 have been prepared in accordance with
generally accepted accounting principles for interim financial information and
the rules and regulations of the Securities and Exchange Commission.
Accordingly, they do not include all of the information and footnotes required
by generally accepted accounting principles for complete financial statements.
However, the information reflects all adjustments (consisting only of normal
recurring adjustments) that, in the opinion of management, are necessary to
present fairly the financial position and results of operations for the periods
indicated.

     The accompanying consolidated condensed financial statements should be read
in conjunction with the audited consolidated financial statements and notes
thereto for the years ending December 31, 1998 and 1997 contained in California
Steel Industries, Inc.'s Registration Statement on Form S-4 (File number 333-
79587) filed with the Securities and Exchange Commission on May 28, 1999.

2.   New Accounting Pronouncements
     -----------------------------

     In June 1998, the Financial Accounts Standards Board issued Statement of
Financial Accounting Standards No. 133, "Accounting for Derivative Instruments
and Hedging Activities" ("SFAS 133").  SFAS 133 establishes accounting and
reporting standards for derivative instruments, including derivative instruments
embedded in other contracts, and hedging activities.  SFAS 133 is effective for
all fiscal quarters of fiscal years beginning after June 15, 2000.  Application
of this accounting standard is not expected to have a material impact on our
financial position, results of operations or liquidity.

3.   Inventories
     -----------

     Inventories are stated at the lower of cost (determined under the last-in,
first-out method of accounting) or market value.

<TABLE>
<CAPTION>
                                                                 June 30, 1999         December 31, 1998
                                                                (In thousands)          (In thousands)
                                                           -----------------------------------------------
<S>                                                           <C>                   <C>
Finished goods.............................................          $ 38,419                  $ 45,641
Work-in-process............................................            21,926                    25,503
Raw materials..............................................            89,652                    96,552
Other......................................................             5,389                     5,700
                                                                     --------                  --------
    Total..................................................          $155,386                  $173,396
                                                                     ========                  ========
</TABLE>

4.   Long-Term Debt
     --------------

     On April 6, 1999, we issued an aggregate of $150,000,000 of ten-year 8.5%
senior unsecured notes. Interest is payable on the notes on April 1 and October
1, commencing October 1, 1999. The notes are senior in right of payment to all
of our subordinated indebtedness and equal in right of payment to all of our
existing and future indebtedness that is not by its terms subordinated to the
notes. We may redeem the notes at any time after April 1, 2004. The indenture
governing the notes contains covenants that limit our ability to incur
additional indebtedness, pay dividends on, redeem or repurchase capital stock
and make investments, create liens, sell assets, sell capital stock of certain
of our subsidiaries, engage in transactions with affiliates and consolidate,

                                       8
<PAGE>


merge or transfer all or substantially all of our assets and the assets of
certain of our subsidiaries on a consolidated basis.

     Proceeds from the notes were used to permanently repay outstanding bank
debt under a $10,000,000 term loan provided by The Dai-Ichi Kangyo Bank,
Netherlands, and a $50,000,000 revolving credit facility and a $80,000,000 term
loan, both provided by a syndicate of institutions led by the Industrial Bank of
Japan, Ltd., Los Angeles Agency.

5.   Dividend Payments
     -----------------

     The Company's board of directors approved and declared a dividend in the
amount of $8,631,000 for common and preferred stockholders.  On April 30, 1999,
$6,848,000 was paid to holders of preferred stock and $1,783,000 to common
stockholders.

                                       9
<PAGE>


                                   SIGNATURES

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


August 27, 1999
                              CALIFORNIA STEEL INDUSTRIES, INC.



                              By:  /s/ Vicente B. Wright
                                   -----------------------------------------
                                       Vicente B. Wright,
                                       Executive Vice President, Finance
                                       (Principal Financial and
                                       Accounting Officer)

                                      10