We assayed 38 middle ear effusions from 23 children aged 4-13 years (mean 7) undergoing tympanostomy tube placements. All fluid was assayed for tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta, IL-8, and IL-10. Cytokine concentrations were measured by means of an enzyme-linked immunosorbent assay. Detectable levels of IL-1beta, IL-8, and IL-10 were found in all of the effusions. TNF-alpha was detected in 18 of the middle ear effusions (47.4%). The mean concentration of TNF-alpha, IL-1beta , IL-8, and IL-10 was, respectively, 0.423 +/- 1.39, 30.58 +/- 68.7, 7001.9 +/- 6743, and 56 +/- 58.7 pg/ml. There was a strong, statistically significant correlation between the concentrations of TNF-alpha and IL-1beta (r = 0.87, P = 0.001) and between IL-1beta and IL-8 (r = 0.53, P = 0.001). There was no correlation between the concentrations of IL-10 and other cytokines examined or between tympanic membrane pathology and the concentrations of TNF-alpha, IL-1beta , IL-8, or IL-10. The presence of IL-10 in middle ear effusions may be one of the causes of a lack of clinical features of acute inflammation and may lead to a chronic inflammatory state.