This study analyzes parent and professional organizations' effectiveness in national special education policy from 1975 to the present. Of specific interest are the relationships between groups' policy victories, how groups construct their political messages, and organizational characteristics. The research is significant in that it is one of the first major studies of education client groups that examines group effectiveness over several decades. Drawing from coded Congressional testimonies and elite interviews with policy makers and organizational leaders, the major findings indicate that problem definition--how groups frame their interests, portray students with disabilities, and narrate their policy stories--is a significant determinant of effectiveness overriding group resources. The implications for policy formulation are discussed. (Contains 5 tables and 10 notes.)