As a possible cancer preventive agent, green tea has been the subject of considerable interest over the past 10 years. Laboratory studies on tea have revealed consistent inhibitory effects against carcinogenesis in a variety of organs in rodents. Both green tea and black tea are known to contain polyphenols and other antioxidant compounds, which may be anticarcinogenic, whereas extracts of tea have blocked nitrosamine-induced cancer in experimental animals. Despite such clear indications from laboratory studies, the association between tea drinking and human ovarian cancer was inconclusive. Such inconsistency may be attributed to differences in tea types and duration of habitual tea consumption in various study populations or because of a lack of control for confounding factors. A lack of detailed and specific information on tea consumption also limited the conclusion drawn by previous studies.