The evolution of national environmental organizations over the past two decades is analyzed, with special attention given to the major organizations that engage in lobbying. The rapid growth experienced by the older organizations and the emergence and subsequent growth of several newer organizations are described. An overview of the activities of these national organizations (including a description of their relationships with one another) is given. Next, the high level of public support for their goals, the unique characteristics of environmental issues, and the efficacy of direct mail recruitment techniques are highlighted as key causes of the organizations’ growth and success. Finally, the organizational consequences of these trends, in the form of staff professionalization and bureaucratization, for the national organizations are examined in some detail.