Ten study populations sampled from a total of 86 communities in a rural Ethiopian area, have been registered and followed for a period of four years. A baseline census revealed a median age of 15 years, a literacy rate of 24%, poor housing and environmental conditions, and low utilization of the existing health care facilities. A surveillance system was established which made it possible to estimate the occurrence of vital events. This showed a crude birth rate of 40.3/1000, a crude death rate of 16.4/1000, a life-expectancy at birth of 48 years, an infant mortality rate of 114/1OOO, a yearly child (1-4 years) mortality rate of 36/1OOO, and an under-five mortality rate of 210/1oOO. The implications of these data in terms of the planning and operations of research and health services are discussed, and on-going and projected studies.