Plant sterols are substances present in vegetable oils, corn and some fruits. According to previous studies, phytosterols are protective in colon carcinogenesis. This case-control study was carried out in order to establish a possible protective role of plant sterols in lung carcinogenesis. The study was performed in Montevideo, Uruguay, during 1993-1996, and included 463 cases with lung cancer and 465 hospitalized controls. Total plant sterol intake was associated with a reduction in risk of 50% when contrasting the upper exposure quartile with the lower, after controlling for major confounders, including tobacco smoking and total energy intake. This protective effect was specially evident in adenocarcinoma of the lung (OR 0.29, 95% CI 0.14-0.63). Therefore, plant sterol intake appears to be an important variable in lung carcinogenesis. Further studies are needed in order to replicate the present findings.