This study examined the bacterial pathogens and the presence of possible risk factors for the development of chronic otitis media with effusion (OME) in a group of Alaska Native children. Middle ear aspirates were collected from 128 children < 6 years of age requiring tympanocentesis between 1987 and 1989. Bacterial pathogens were cultured from 40% of 209 fluids. Predominant isolates, after contamination of the outer ear was controlled for, were Haemophilus influenzae (21%; 84% of these were nontypeable), Streptococcus pneumoniae (8.1%; serotypes 6B, 10A, 11A, 14, 18B, 18C, 19A, and 23F), Staphylococcus epidermidis (3.8%), and Moraxella (Brahmanella) catarrhalis (2.9%). Pneumococcal-C-polysaccharide (PnC) was detectable in 3 of 135 (2.2%) aspirates that did not grow Streptococcus pneumoniae. Combining culture and PnC assay results evidence of pneumococcal infection was found in almost 10% of aspirates tested. There was not a significant difference in the number of episodes of acute otitis media after the first year of life based on the age at the first episode (< 6 mo, > or = 6 mo). However, 88% of infants in the study had their first acute otitis media episode before 1 year of age.