Millions of children in developing countries are dying from diseases that could be prevented or treated by simple interventions. To examine ways to improve the delivery of these basic services, we evaluated well child clinics and mass vaccination campaigns under operational conditions in a rural area of Nicaragua. We found that mass vaccination campaigns using volunteers reached 77.1 per cent of the population under age six. At stationary well child clinics in which villages were invited to a health center and a small food ration was used as an incentive, attendance improved to 94.1 per cent. Similar attendance levels (99.2 per cent) were attained by mobile well child clinics also using a food incentive. Attendance at stationary clinics decreased with the distance of the village from the health center. However, stationary clinics took up only half as much health workers' time as mobile clinics. Our results suggest that stationary clinics employing food as an incentive could be used for villages or neighborhoods close to a health center while mobile clinics offering food should be reserved for more isolated villages.