Since the mid-1930s in the Senate and the late-1.960s in the House, members of Congress have been permitted to cosponsor legislation. Many members have become very active in cosponsoring legislation, while others have shown some reluctance. This article investigates several possible reasons for differing levels of cosponsorship activity. The goals of securing re-election, gaining influence within the Congress, and producing good public policy, as well as the member's general level of legislative activity, are examined as influences on cosponsorship activity. The findings indicate that the representative's cosponsorship activity is influenced by ideology (the representative's measure of good public policy), by the representative's general level of legislative activity, and by the representative's re-election prospects if in the Senate and seniority if in the House.