How do organized interests select the Supreme Court cases in which to file amicus curiae briefs? Starting with the assumption that organized interests pursue policy influence, I argue that an organized interest will submit amicus curiae briefs in the cases that provide the greatest opportunity for the interest to influence the content of the majority opinion. Membership-based interests, however, will also have to consider the effect of their case-selection decisions on their ability to attract and retain membership support. I test my hypotheses with data on a large sample of organized interests and their amicus curiae brief filings in the 1991-1995 Supreme Court terms. The results of this analysis provide support for my hypotheses and indicate that organized interests seek out cases in which the justices are relatively information-poor. Membership-based interests also choose cases that allow for visible and apparently “successful” participation.