The ability of a medical self-care program to have an impact on the utilization and cost of in-clinic and referral visits in a prepaid group practice was studied by following the medical encounter records of 900 HMO members in 217 families during a 12-month period. A control group selected by randomization after acceptance of an initial invitation to participate was employed. In spite of the program's impressive effect on both self-care knowledge and per-visit costs, the study could not demonstrate any significant program effect either on the frequency or on the total costs of clinic visits.