In 1996, the Advisory Committee on Immunization Practices, the American Academy of Pediatrics, the American Association of Family Physicians, and the American Medical Association recommended a routine health-care visit for adolescents aged 11-12 years. During this visit, adolescents not fully vaccinated should receive up to four recommended vaccines (hepatitis B, a measles-containing vaccine [MCV], varicella, and tetanus-diphtheria) and other preventive services and counseling. Because many adolescents are not up-to-date for all of these vaccines, 43 states have developed middle school entrance requirements or laws for one or more of these vaccines. Since 1997, CDC, in collaboration with the Pre-Teen Health Project in San Diego, California, has evaluated the impact of the state's middle school vaccination law, which requires students entering seventh grade on or after July 1, 1999, to have documented receipt of three doses of hepatitis B and two doses of MCV or to have obtained a written exemption based on personal beliefs or medical grounds. This report summarizes the results of that analysis, which indicate that when school entrance requirements are enforced, high vaccination coverage can be achieved.