Three case studies of interorganizational collaboration between regional education agencies (REAs) and school districts illustrate how successful knowledge utilization occurs. Researchers studied how knowledge utilization services in four areas--staff development, linking agent assistance, information retrieval, and broad organizational issues--were supplied to their school districts by the Wayne County (Michigan) Intermediate School District, the Northern Colorado Educational Board of Cooperative Services, and the Educational Improvement Center-South (New Jersey). For each case study, data were collected from REA documents, field observation, and field interviews with staffpersons from the REA, school districts, and the state education agency. Results showed that successful interorganizational collaboration could be explained by six factors: (1) services were user-oriented; (2) services were supported by external resources; (3) REA and district staffs formed active interpersonal networks; (4) the state mandated collaboration; (5) collaboration yielded mutual benefits for REAs and school districts; and (6) federal and state regulations and policies facilitated cooperation. To test these explanations, further research is needed on other types of interorganizational arrangements and on knowledge utilization itself. Appended to the report are data on all states' REAs and a copy of the field questionnaire. (Author/RW)