Why do firms participate in the EPA's voluntary environmental programs? Possible reasons include: (1) to appeal to consumers who demand ‘green’ products; (2) to preempt government regulation; (3) to seek regulatory relief from the agency; and (4) to gain a competitive advantage over competitors. This article examines the determinants of participation in voluntary environmental programs, focusing on testing hypotheses 1 and 3. To test 2, a different approach is used than in previous literature. The focus is on a specified universe of firms (manufacturing firms in the Standard & Poor 500), and their participation in each of three EPA voluntary programs (33/50, Green Lights, and WasteWi$) referring to differently regulated pollutants is analyzed. Our empirical analyses reveal that (1) publicity is an important component of participation; (2) the worse the environmental track record of the firm, the more likely the firm is to participate, but only in programs directly related to highly regulated pollutants; and (3) firms that scrutinize their environmental performance more carefully are wary of newer programs with uncertain reach of the public and uncertain benefits. Firms appear to value the information/technology transfer aspect of joining a program.