During the period from January 1988 to December 1994, a case-control study that included 497 cases of lung cancer and 497 controls was carried out at the Instituto de Oncologia, Montevideo, Uruguay, to evaluate the relationship between the drinking of mate (a local tea prepared with infusions of the herb Ilex paraguariensis) and the risk of lung cancer in men. Mate drinking has been associated with risk of most upper-aerodigestive tract cancers. After adjusting for major covariates, including pack-years of cigarette smoking, the amount of mate was associated with a 1.6-fold increase in risk for heavy drinkers, compared with light drinkers, with a significant dose-response pattern. When the analysis was performed by cell type, small cell lung cancer showed a significant increase in relative risk for mate amount (odds ratio, 2.9; 95% confidence interval, 1.3-6.2) and mate duration (odds ratio, 3.6; 95% confidence interval, 1.3-9.9). On the other hand, pulmonary adenocarcinoma was not associated with mate drinking. Possible reasons for these results are discussed, and areas for future research are suggested.