Despite the growing importance of voluntary programs as tools for environmental management, they have been subject to quite limited evaluation. Program evaluation in the absence of randomized experiments is difficult because the decision to participate may not be random and, in particular, may be correlated with the outcomes. The present study is designed to overcome these problems by gauging the environmental effectiveness of two voluntary climate change programs—the U.S. Environmental Protection Agency’s Climate Wise program and the U.S. Department of Energy’s Voluntary Reporting of Greenhouse Gases Program, or 1605(b)—with particular attention to the participation decision and how various assumptions affect estimates of program outcomes. For both programs, the analysis focuses on manufacturing firms and uses confidential census data to create a comparison group and to measure outcomes (expenditures on fuel and electricity).Overall, we find that that the effects from Climate Wise and 1605(b) on fuel and electricity expenditures are no more than 10 percent and probably less than 5 percent. Virtually no evidence suggests a statistically significant effect of either Climate Wise or 1605(b) on fuel costs. Some evidence suggests that participation in Climate Wise led to a slight (3–5 percent) increase in electricity costs that vanished after two years. Stronger evidence suggests that participation in 1605(b) led to a slight (4–8 percent) decrease in electricity costs that persisted for at least three years.