The Combatting Childhood Communicable Disease (CCCD) project is a comprehensive public health programme designed to reduce child mortality by 25% through the use of the following strategies: vaccination, oral rehydration therapy, and prompt treatment for malaria. To evaluate this programme, cross-sectional surveys were conducted in neighbouring health zones in Zaire in 1984 to determine the use of selected medical services by the population and to estimate the child mortality rate before the CCCD programme began. A reinterview survey was conducted on a subsample of women previously interviewed to determine the reliability of the mortality estimates. In both health zones 84-85% of women used antenatal services, 45% of children under age 6 who had had fewer were treated with an anti-malarial drug, 19-22% of children age 12-23 months had been vaccinated against measles, and virtually no children who had had diarrhoea were treated with oral rehydration therapy. Women's underreporting of births and deaths resulted in low estimates of mortality in both surveys. The reinterview survey provided more accurate estimates of mortality and led to a better understanding of the factors influencing underreporting. The estimated infant mortality rate was 74 deaths per 1000 livebirths; and the probability of dying before age 5 was 191 per 1000. Because births and deaths reported with incomplete dates were excluded from analysis, the mortality rates from the reinterview survey are underestimates. Given the difficulty in obtaining accurate estimates of mortality, primary importance should be given to developing and improving routine health information systems that measure changes in health status and provide information to evaluate programmes.