This paper reviews the history and present status of red tide and algal toxins occurrence in Hong Kong and Pearl River Estuary. As one of the most frequent HAB occurrence areas, Hong Kong first began its reporting of HAB events in the early 1970's. In 1983, Lam & Ho pointed out that the increasing HAB and related fish-killing events in Hong Kong were correlated with increased urbanization of that region. From 1980～1997, 496 HAB events were recorded in Hong Kong waters. According to the record, the most f...