To identify substances with anti-human immunodeficiency virus (HIV) activity in traditional medicines, 101 extracts of Korean medicinal plants were screened for their inhibitory effects on HIV type 1 protease (PR). The enzyme activity was determined by HPLC. Of the extracts tested, strong inhibitory effects were observed in the acetone extracts of the pericarp and leaves of Camellia japonica, the water extract of the leaves of Sageretia theezans and the methanol extract of the aerial part of Sophora flavescens. Camelliatannin H from the pericarp of C. japonica, showed a potent inhibitory activity on HIV-1 PR with IC50 of 0.9 muM. Copyright (C) 2002 John Wiley Sons, Ltd.