Objective: The aim of our study was to contribute to the literature about the prevalence of OME by conducting a research in a wide geography examining most of the associating factors together with a questionnaire. Additionally, possible effects of altitudes and latitudes, concordance between the otoscopic examination findings and tympanometric and acoustic reflex test results were evaluated in 4-7 years old children in the same season in different countries. Methods: In the randomly sampled schools from different regions of different cities where people of different scoioecomonic statuses live, 4-7 year-old children were included in the study. The results of the questionnaire covering the potential factors in OME etiology were evaluated together with the results of the otoscopic examination and tympanometry findings, and also the acoustic reflex findings to direct the interpretation in cases of low amplitude -blunted peak tympanograms which can be interpreted as a "Type B" or "Type As". All the results were gathered in the same season.