A measles vaccination coverage of between 50 and 60% has been achieved in Kinshasa, Zaire, from 1980-1985. During that interval, the annual number of measles cases and the incidence rate of measles reported by a surveillance system remained similar, and measles epidemics occurred in alternating years. The estimated number of measles cases in Kinshasa is 87,600 per year. Of reported measles cases, 27% occurred in children under nine months of age, younger than the recommended age at vaccination. Two results expected in a partially vaccinated population, a reduction in measles incidence greater than the level of vaccination coverage and a shift in the age distribution of measles to older children, have not been observed. Measles control in Kinshasa will require a vaccination coverage of higher than 60%. In addition, given the age-specific risk of measles infection here, a measles vaccine that would be effective when given before nine months of age would be an important element in controlling measles transmission. Because the epidemiology of measles in Kinshasa is a likely consequence of its urban environment, such a vaccine would represent a significant advance toward the control of measles in urban Africa.