The epidemiologic literature in the English language regard- ing intake of tomatoes and tomato-based products and blood lycopene (a compound derived predominantly from toma- toes) level in relation to the risk of various cancers was re- viewed. Among 72 studies identified, 57 reported inverse associations between tomato intake or blood lycopene level and the risk of cancer at a defined anatomic site; 35 of these inverse associations were statistically significant. No study indicated that higher tomato consumption or blood lycopene level statistically significantly increased the risk of cancer at any of the investigated sites. About half of the relative risks for comparisons of high with low intakes or levels for toma- toes or lycopene were approximately 0.6 or lower. The evi- dence for a benefit was strongest for cancers of the prostate, lung, and stomach. Data were also suggestive of a benefit for cancers of the pancreas, colon and rectum, esophagus, oral cavity, breast, and cervix. Because the data are from obser- vational studies, a cause–effect relationship cannot be estab- lished definitively. However, the consistency of the results across numerous studies in diverse populations, for case– control and prospective studies, and for dietary-based and blood-based investigations argues against bias or confound- ing as the explanation for these findings. Lycopene may ac- count for or contribute to these benefits, but this possibility is not yet proven and requires further study. Numerous other potentially beneficial compounds are present in toma- toes, and, conceivably, complex interactions among multiple components may contribute to the anticancer properties of tomatoes. The consistently lower risk of cancer for a variety of anatomic sites that is associated with higher consumption of tomatoes and tomato-based products adds further sup- port for current dietary recommendations to increase fruit and vegetable consumption. [J Natl Cancer Inst 1999;91: 317–31]