To determine the incidence of otitis media (OM) and the bacteriology of acute otitis media (AOM) in a clinic population of young children in Pittsburgh, 138 black infants and 60 white infants were followed from birth to 2 years of age, examined at monthly intervals and whenever an upper respiratory tract infection (URI) or OM intervened. By 24 months of age the cumulative incidence of episodes of AOM was 43% and 42%, and of episodes of middle-ear effusion (MEE) was 86% and 85% in black and white infants, respectively. The average rate of episodes of AOM was 0.41 and 0.39 and of episodes of MEE was 1.68 and 1.70 in black and white infants, respectively. Tympanocentesis was performed for episodes of AOM and the following organisms were isolated from black and white infants, respectively: Streptococcus pneumoniae 43% and 43% of episodes; Moraxella catarrhalis 24% and 24%; non-typable Haemophilus influenzae 18% and 24%; and Haemophilus influenzae type b 5% and 0%. In both black and white infants first born children had less ear disease. We found no difference in the incidence of otitis media during the first 2 years of life between black and white infants.