OBJECTIVES: This study examined the frequency of requests that state health departments investigate cancer clusters, the nature of those requests, and the resources available for the investigations. METHODS: A mail survey was sent to state health departments requesting data for 1997. RESULTS: Approximately 1100 cluster investigation requests were made in 1997. Most requests were made by citizens, and no pattern emerged for types of cancer or hazards suspected. States rate this work as average in importance and feel satisfied with the successfullness of their communication efforts. CONCLUSIONS: Few cluster inquiries require further investigation. Nonetheless, this interaction represents resources well spent in terms of public service and education.