Samples of middle ear effusions from 102 children with serous and mucoid otitis media were cultured for mycoplasmas and bacteria. No sample yielded mycoplasmas but bacteria were cultured from 48 (47 per cent). Organisms commonly regarded as pathogens were present in 25 samples (Haemophilus influenzae 17, Streptococcus pneumoniae four, other streptococci four). The only sample from which anaerobic bacteria were isolated was from a patient with cholesteatoma.