In 1976 the recommended time for routine measles immunization was changed from 12 to greater than or equal to 15 months of age. Because of the known decrease in compliance with immunizations given during the second year of life and the scheduling of an additional visit close to the time of the diphtheria-tetanus-pertussis (DTP) booster immunization, the potential benefit from this change might be offset by a decrease in compliance in securing both measles vaccination and DTP booster immunization. A study of the change in immunization compliance was carried out in a county health facility and in a prepaid medical group practice. Charts of 795 infants (395 born before and 400 born after the change) were reviewed to assess the rates of compliance with measles and with DTP immunizations. Administration of measles vaccine at a scheduled time decreased by 10% (0.05 less than P less than 0.06) at the public health facility after the change in 1976 and by 13% at the prepaid group practice (P less than 0.01). This difference evened out in the public health facility patients by age 2 years, but a 9% decrease was still apparent at the prepaid medical group. A similar pattern was seen in compliance with the DTP booster immunization at each site. Any benefit derived by an increased measles seroconversion rate apparently was offset by an overall decrease in compliance for both measles and DTP booster immunizations.