While there has been a substantial body of research on interest group activity in U.S. federal courts, there has been comparatively little analysis of interest group engagement with state courts. Given that state courts adjudicate the vast majority of cases in the American legal system and very few cases are appealed to the Supreme Court, understanding why organized interests participate in these courts is of great importance. The present study analyzes interest group involvement as amicus curiae in all state courts of last resort from 1995-1999 to examine what factors motivate organized interests to turn to the courts. The results indicate that interest groups are primarily motivated by their policy goals in deciding which cases to file amicus briefs in, but that they are limited in their ability to file by institutional constraints unique to state courts of last resort. This research provides insight into interest group behavior, state courts and the role organized interests play in influencing legal outcomes in the American states.