Background There are racial differences in the prevalence and types of androgenetic alopecia (AGA). There have been several reports on the prevalence and types of AGA in the general population of caucasians, but few studies on Koreans with samples of sufficient numbers have been reported.Objectives To obtain a more precise estimate of the prevalence and types of AGA in Korean men and women and to compare the results with those in caucasians.Methods The prevalence and types of AGA were analysed in 10,132 Koreans (5531 men and 4601 women) who had visited the Health Examination Centre at Kyung Hee University Hospital for regular health examinations between December 1997 and July 1999. To classify the degree of hair loss for each subject, the Norwood classification was used in men and the Ludwig classification in women. For AGA in men, ‘female pattern’ was added to the Norwood classification.Results In Korean men, the prevalence of AGA (Norwood III or above) at all ages was 14·1%. It increased steadily with advancing age, but was lower than that of caucasians: 2·3% in the third decade, 4·0% in the fourth decade, 10·8% in the fifth decade, 24·5% in the sixth decade, 34·3% in the seventh decade and 46·9% over 70 years. Type III vertex involvement was the most common type in the third decade to the seventh decade; over 70 years, type VI was most common. A ‘female pattern’ was observed in 11·1% of cases. In Korean women, the prevalence of AGA (Ludwig I or above) at all ages was 5·6%. It also increased steadily with advancing age: 0·2% in the third decade, 2·3% in the fourth decade, 3·8% in the fifth decade, 7·4% in the sixth decade, 11·7% in the seventh decade and 24·7% over 70 years. Grade I was the most common type up to the sixth decade; over 60 years, grade I and II were similar in prevalence. Grade III (total baldness) was not observed. A family history of baldness was present in 48·5% of men and 45·2% of women with AGA.Conclusions The prevalence of AGA in Korean men and women was lower than that in caucasians, as recorded in the literature. Korean men tend to have more frontal hairline preservation and show a more ‘female pattern’ of hair thinning than caucasians. Therefore, ‘female pattern’ should be added to the classification of AGA.