Editors' Summary: The Clean Air Act Amendments of 1990 finally became law on November 15, 1990. The Amendments, the first major revision of the Clean Air Act since 1977, include titles on nonattainment areas, mobile sources, hazardous air pollutants, acid rain, and stratospheric ozone protection. Two other titles—the permits and enforcement titles—will be vital to the implementation of the revised Clean Air Act. The full potential of the Act cannot be realized without effective enforcement power and an efficient permit program. The author, a principal participant in developing the permit and enforcement titles in the Senate, discusses the key elements of these titles. He highlights the differences in the House and Senate bills and how they were reconciled in the Conference Committee. The Article also discusses several important permitting and enforcement issues that must be resolved by EPA and others in the process of implementing the Amendments. The author concludes that the success of the permits title will be largely shaped by EPA's permit regulations scheduled for November 1991. The effectiveness of the enforcement title will be established over the next few years as the government uses the new weapons in its enforcement arsenal.