EXHIBIT 32.1

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the quarterly report of Mittal Steel USA ISG Inc.(the
"Company") on Form 10-Q for the period ended June 30, 2005, as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), each of
the undersigned officers of the Company certifies, pursuant to 18 U.S.C.
Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of
2002, that, to such officer's knowledge:

          (1)     The Report fully complies with the requirements of Section
                  13(a) or 15(d) of the Securities Exchange Act of 1934; and

          (2)     The information contained in the Report fairly presents, in
                  all material respects, the financial condition and results of
                  operations of the Company as of the dates and for the periods
                  expressed in the Report.

A signed original of this written statement required by Section 906 has been
provided to the Company and will be retained by the Company and furnished to the
Securities and Exchange Commission or its staff upon request.

Date:  August 16, 2005

                                                       /s/ Lou Schorsch
                                                       -------------------------
                                                       Lou Schorsch
                                                       Chief Executive Officer
                                                       Mittal Steel USA ISG Inc.


                                                       /s/ Bhikam C. Agarwal
                                                       -------------------------
                                                       Bhikam C. Agarwal
                                                       Chief Financial Officer
                                                       Mittal Steel USA ISG Inc.

The foregoing certification is being furnished solely pursuant to 18 U.S.C.
Section 1350 and is not being filed as part of the Report or as a separate
disclosure document.