A nation-wide survey was conducted to estimate the prevalence of otitis media(OM) and allied diseases through physical examination by otolaryngologic doctors from July to October, 1991. A sample study population was selected from a panel to be representative of the Korean pupulation by multistage clustered and stratified random sampling method based on the national census data, 1990. Total subjects examined were 9,321, who were drawn from 2,899 house-holds residing in 60 different areas throughout the country. The overall prevalence of OM was 2.85%(3.10% of males and 2.61% of females). The prevalence of each subtype was as follows : acute otitis media(AOM), 0.02% ; middle ear effusion(MEE), 0.60% ; and chronic otitis media(COM), at 2.19%, respectively. For COM, non-cholesteatomy type included 78% of the cases, while COM with cholesteatoma yielded 22%. Chronic adhesive OM was 9% of COM, which was regarded as one of the non-cholesteatoma types. The prevalence of OM did not vary by sex, nor by urban-rural difference. There was an increasing tendency for prevalence of OM by age. However, the prevalence of both MEE and AOM showed a decreasing pattern with increasing age. Particularly noteworthy was a significant geographic variation in the prevalence of OM by province. The prevalence rate of nasal septal deviation(NSD) was 21.93% and the presence of NSD was significantly related to that of OM(p<0.05). The prevalence rates of nasal allergy symptoms, nasal polyposis and evident cleft palate were 1.14%, 1.00% and 0.07%, respectively. The presence of OM was significantly correlated with both nasal allergy symptoms(p<0.1) and evident cleft palate(p<0.05) but not with that of nasal polyposis.