Editors' Summary: On January 7, 1983, the D.C. Circuit decided Duquesne Light Co. v. Environmental Protection Agency, turning back sweeping industry challenges to EPA's Clean Air Act §120 noncompliance penalty regulations. The Comment reports that the rules' broad coverage and narrow exemptions, streamlined administrative procedures, and methodology for calculating penalties equal to the economic benefits of delayed compliance all survived the court's scrutiny. The court remanded the rules on only three relatively minor, though not insignificant, points. However, the court victory must be viewed in the context of the Agency's unchallenged assertion of discretion to impose §120 penalties on only a fraction of those facilities that are liable. The Comment concludes that §120 will see expanded use in the aftermath of Duquesne Light, but that it is too early to tell how far the expansion will carry.