To study the possible association between drinking tea and lung cancer, epidemiological and experimental materials were collected from the Chinese population in Hong Kong. In a retrospective study of 200 female lung cancer patients and 200 matched controls, all subjects were interviewed concerning their eating habits, smoking histories, and lifetime exposures to environmental pollutants. Analysis of the data demonstrated an adjusted and statistically significant increased lung cancer risk of 2.7 among those who drank green tea. Several brands of tea commonly drank in Hong Kong were assayed for mutagenicity using Ames' assay. Significantly elevated levels of mutagenic activity were found to be present after metabolic activation using cell-free extracts of cecal bacteria from rats. These data suggest that further research is needed to understand the possible consequences to human health of ingestants taken at low doses but long duration over the normal lifespan, and the possible interactive effect between mutagens in tea and other ingestants and inhalants in human cancer etiology.