The use of voluntary approaches to achieve environmental improvements has grown dramatically in the United States since they were first introduced thirteen years ago. As of 2004, there are over 50 voluntary programs in the U.S. at the federal level alone. These programs take a variety of forms, from large, cross-industry efforts to reduce global climate impacts to smaller, “boutique” efforts aimed at specific industrial sectors. Other voluntary approaches used in the U.S. include negotiated agreements, industry-initiated unilateral commitments, and state and regional voluntary initiatives, but these tend to be used less regularly. Despite the diversity of voluntary approaches in the U.S., they often pursue common, and sometimes overlapping environmental objectives and use similar methodologies to achieve such goals. While most voluntary initiatives in the U.S. state an explicit environmental goal, they may also have less direct policy objectives such as enhancing innovation or increasing awareness of environmental issues. In addition, information about firm participation or environmentally responsible products and products is sometimes shared with consumers. Many argue in favor of the increased use of voluntary approaches in environmental policymaking on the basis of environmental effectiveness, economic efficiency, reductions in government administrative, monitoring and enforcement costs, increases in environmental awareness, and encouragement of innovation. Few programs have been evaluated properly on the basis of these objectives, however. The empirical literature sheds little light on the value of voluntary approaches in achieving goals set by U.S. environmental policy. The difficulty in evaluating voluntary approaches lies in sorting through the myriad of programs, identifying a discernible environmental goal, gathering adequate data for analysis, and measuring achievement of the environmental goal relative to a reasonable baseline scenario.