Nearly every state in the United States has developed one or more voluntary cleanup programs (VCPs) to support an alternative approach to cleanup of contaminated sites. Thousands of sites have entered into these programs. Yet, despite the ubiquity of VCPs and the number of enrolled properties, we know little about the factors that influence voluntary action at these sites. This paper reports results from interviews of state officials involved in VCPs in all states, and from a survey of VCP participants in several states. It has two objectives. First, at an application level, the interview and survey results can be used to help improve policy and practice in voluntary cleanup programs. Second, the paper furnishes a unique study to the general literature on environmental voluntary behavior, contributing an empirical, survey-based study of volunteers engaged in cleanup.