PURPOSE To identify physicians' and parents' perceptions of barriers to completing the immunization process by age 24 months. METHODS A questionnaire hand-delivered to 110 physicians who treat children yielded a response rate of 83%. A telephone survey conducted with parents of a random sample of 2,100 children younger than three years of age selected from the county birth records yielded an adjusted response rate of 87%. RESULTS Physicians' response fell into two categories: those with more and less than 90% up-to-date immunizations. Those with less than 90% indicated that parental knowledge is the primary reason. Those with more than 90% reported telephone follow-up for missed appointments. The top three barriers reported by parents; (1) waiting time at the clinic (33%), (2) child too ill at time of appointment (21%), and (3) insurance does not cover immunizations (16%). CONCLUSIONS There is an opportunity for education intervention with physicians, policy makers, and parents in several key areas: (1) fact-based contraindications to immunizations, (2) effective means of follow-up, (3) accessibility to immunization for the under-insured, and (4) parental responsibility.