In N'Djamena, capital of Chad, measles vaccination coverage of 12–23-month-old children fell from 61% in 1990 to 15% in 1993. A community survey of measles after an outbreak in 1993 showed that among children < 5 years of age, the mean monthly attack rate was 37 per 1000 (95% CI, 32–43) and the mean case fatality rate was 7·4%. Measles incidence was highest (77/1000/month) in children aged 9–11 months and fell among children > 3 years of age. Incidence rates were high (56/1000/month) among 6–8-month-old children, but only 3 deaths occurred in this age group. Measles vaccine efficacy, estimated by comparing attack rates in unvaccinated and vaccinated children, was 71 % (95% CI, 59–80%). Extrapolation of the results to the city population indicated that an estimated 19000 cases and > 1000 measles-associated deaths occurred in 1993. This preventable morbidity and mortality, in a city where coverage was formerly among the highest in Africa, shows the need for sustained global commitment to preventive health care.