To determine the value of different pneumotoscopic findings in diagnosing the middle ear effusion (MEE) of acute (AOM) and non-acute otitis media, 11,804 ear-related visits of 2,911 unselected children at ages 0.5-2.5 years were analysed. About half of these were examined by an otolaryngologist in one, and half by a pediatrician in another, urban area. Myringotomy was always performed when MEE was suspected, and it confirmed the presence of MEE in 85% (otolaryngologist) and 82% (pediatrician) of altogether 5,462 acute and in 69% (both doctors) of 1,092 non-acute cases suspected. Redness of the tympanic membrane (TM) was found in only 18% and 27% of the visits with AOM, and it predicted MEE with only 60% and 51% probability, if seen in acute visits. Cloudiness of the TM was noticed in 81% and 67% of the visits with AOM; its specificity and the other calculated variables were good in regard to the diagnosing of MEE, especially in acute cases in both groups. Distinctly impaired mobility of the TM was of about the same diagnostic value, but its position reliably indicated MEE only when bulging. In AOM the colour or mobility of the TM was normal very rarely, but the position was normal in a third of the cases. Thus, although there were differences in the incidences of different otoscopic findings in the two study groups, the diagnostic value of certain pneumatic otoscopic findings, especially cloudiness and distinct hypomobility of the TM, seemed to be good in both groups.