Objective: To describe current immunization requirements and policies in North American medical schools both at matriculation and before students begin clinical clerkships. Design: Survey of all allopathic medical schools in the United States and Canada. Participants: One hundred and fifteen medical schools. Measurements and Main Results: Twenty-eight percent of medical schools had no immunization requirements for matriculating medical students. Thirty-one percent of the schools had no rubella immunity requirement, 40% had no measles immunity requirement, and 44% had no polio immunity requirement for matriculating students. For students beginning clinical clerkships, 18%, 35%, and 40% of schools did not require rubella, measles, and polio immunity, respectively. Only 19% and 4% of schools required hepatitis B and influenza immunizations, respectively, at any time during training. Between 20% and 30% of schools accepted student self-report as evidence of rubella and measles immunity. Conclusions: Despite expert guidelines, current medical school immunization policies for matriculating medical students are inadequate. Methods to assess, monitor compliance with, and facilitate student immunization are needed. Medical schools should review their immunization policies to comply with published guidelines.