Rather than striving to measure the influence of groups in the policy-making process this article concentrates instead on the ways in which interest groups are created and the means by which they remain in existence. A survey by mail was conducted during 1980-1981 of all voluntary associations that are open to membership and concerned with some aspects of public policy at the national level. The sample of groups was chosen from the Congressional Quarterly's Washington Information Directory. Questionnaires were delivered to 913 interest groups, and usable responses were received from 564, yielding a response rate of 64.8%.