The epidemiology of acute respiratory tract infection (ARI) was investigated in a rural community 80 km north of Nairobi, Kenya. This research was conducted prospectively on 250 families with 470 children <5 years of age who were contacted every 8 days during the 3-year study. The yearly incidence of respiratory tract infections decreased from 5.2 to 3.4 during the>study; <5% of these infections involved the lower respiratory tract. The incidence was inversely related to age, and the illnesses were generally mild and brief in length. Fifteen children died during the study period. The precise causes of death are unknown, but respiratory infections possibly played a role in most cases. This study emphasizes the importance of determining the risk factors responsible for unusually severe morbidity and high mortality in children with ARI in developing countries.