The International Chemical Workers Union is implementing a 3-year nationwide field experiment in cancer prevention education. The educational program includes three stages: generalized cancer control education, education tailored to each local union, and an interactive monitoring system designed to provide ongoing communication and reinforcement for desired cancer control behaviors among local unions and their members. These alternative educational approaches will be systematically evaluated using a randomized factorial study design involving more than 120 local unions. The need for such a program is demonstrated by the results of a needs assessment survey of 690 union members. Respondents expressed strong concern regarding possible carcinogen exposures at the work site, combined with generally low ratings of co-worker knowledge of and adherence to appropriate cancer control behaviors. Engineering controls and personal protective equipment were reported to be inadequate in many work sites.