The Cancer Prevention Reminder System is a computer-based system designed to increase the delivery of periodic health maintenance procedures. The program provides printed reminders that identify patients' overdue procedures, prints summary reports of the percentage of patients who are eligible and overdue for a procedure, and prints mailing labels for patients. We performed a randomized, controlled trial in which the effects of computer-based reminders were compared with those of two other interventions among residents in a university-based group practice.