With widespread use of the live virus vaccines for measles, mumps, and rubella, there has been a dramatic decrease in the incidence of all three diseases. At the same time, an increasing proportion of the remaining cases are occurring in adolescents and adults. Thus, vaccinations for these three diseases of childhood must be included in a comprehensive program for adult immunization. The vaccines have a proven history of safety and efficacy and are usually administered together as combined measles-mumps-rubella (MMR) vaccine. Vaccination for measles, mumps, and rubella is particularly important for susceptible adults likely to come in contact with infected children. Adults at particularly high risk for exposure may include daycare center workers, teachers and other school employees, college students, medical personnel, and those planning to travel outside the United States.