BACKGROUND: Recent predictions of catastrophic epidemic surge of HIV infection in East Asia concern experts and governmental organizations. As in many other areas, countries in East Asia show diversities in their HIV epidemics, both geographically and temporally. However, they have similar regional, cultural and racial characteristics which allow them to have certain common factors. Having a clear picture of the current extent and feature of HIV/AIDS in this region is a very difficult task largely due to the fast pacing of expending epidemic and difficulty in data-sharing among countries in the region. Hence, we decided to study the epidemiologic feature of HIV/AIDS in East Asia through East Asia Network on HIV (EAN-HIV). MATERIALS AND METHODS: The epidemiological patterns of HIV/AIDS in East Asian countries were investigated by collecting data through EAN-HIV. RESULTS: The HIV/AIDS epidemic in East Asia started relatively late at mid 1980s. Since then, the number of newly infected HIV/AIDS cases has been steadily increasing with stiffer escalation in recent years. In China and Taiwan, IDU plays an important part in the swiftly growing HIV epidemics; however, in other regions like Korea, Japan, and Hong Kong, MSM (men who have sex with men) seems to be more of a problem. The major subtypes of HIV in East Asia are subtype B, C, and CRF01_AE, and rapidly evolving circulating recombinant forms (CRF) between subtypes such as CRF07_BC give dynamic change to the current status. CONCLUSION: The incidence of HIV/AIDS is rapidly increasing in East Asia. The epidemic pattern has undergone dynamic changes over time. China seems to be the leading source of HIV/AIDS epidemic in East Asia due to its large population and rapidly growing epidemics.