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                                                                      EXHIBIT 12


                       WILLIAMS COMMUNICATIONS GROUP, INC.

               COMPUTATIONS OF RATIO OF EARNINGS TO FIXED CHARGES
               AND RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND
                      PREFERRED STOCK DIVIDEND REQUIREMENTS


<Table>
<Caption>
                                                                 SIX MONTHS ENDED
                                                                     JUNE 30,
                                                           ----------------------------
                                                               2001            2000
                                                           ------------    ------------
                                                                  (IN THOUSANDS)
<S>                                                        <C>             <C>

Earnings:
  Income (loss) before income taxes                        $   (495,566)   $     32,584
  Add:
    Interest expense -- net                                     201,073          95,627
    Rental expense representative of interest factor             60,210          70,383
    Minority interest in loss of consolidated
       subsidiaries                                             (13,191)         (5,002)
    Equity losses                                                 9,208           7,155
                                                           ------------    ------------
       Total earnings (loss) as adjusted plus fixed
         charges
                                                           $   (238,266)   $    200,747
                                                           ============    ============
Fixed charges and combined fixed charges and
  preferred stock dividend requirements:
    Interest expense -- net                                $    201,073    $     95,627
    Capitalized interest                                         55,662          64,741
    Rental expense representative of interest factor             60,210          70,383
                                                           ------------    ------------
      Total fixed charges                                       316,945         230,751

    Preferred stock dividends and amortization of
      preferred stock issuance costs                              8,765              --
                                                           ------------    ------------
    Combined fixed charges and preferred stock
      dividend requirements
                                                           $    325,710    $    230,751
                                                           ============    ============

Ratio of earnings to fixed charges                                    (a)             (a)
                                                           ============    ============

Ratio of earnings to combined fixed charges and
  preferred stock dividend requirements                               (b)             (b)
                                                           ============    ============
</Table>

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(a)  Earnings were inadequate to cover fixed charges by $555,211,000 and
     $30,004,000 for the six months ended June 30, 2001 and 2000, respectively.

(b)  Earnings were inadequate to cover combined fixed charges and preferred
     stock dividend requirements by $563,976,000 and $30,004,000 for the six
     months ended June 30, 2001 and 2000, respectively.