To examine whether dietary sugar modifies lung cancer risk, a case-control study involving 463 cases with lung cancer and 465 hospitalized controls was conducted in Uruguay in the period 1993-1996. Dietary patterns were assessed in detail using a 64-item food-frequency questionnaire, which allowed the calculation of total energy intake. After adjustment for potential confounders through a model that included tobacco smoking and total energy, total fat, vitamin C, and alpha-carotene intakes, an increased risk for sugar-rich foods, total sucrose intake, sucrose to dietary fiber ratio, and glycemic index for lung cancer was observed (odds ratio for highest category of total sucrose intake = 1.55, 95% confidence interval = 0.99-2.44). When lung cancer was analyzed separately by cell type, odds ratios for small cell and large cell undifferentiated carcinoma were higher than those observed for squamous cell and adenocarcinoma of the lung. The joint effect of pack-years, total fat intake, and sucrose intake was associated with an increased risk of 28.3 (95% confidence interval = 13.4-59.7) for high values of the three variables. The study suggests that high sucrose intake could be an important risk factor in lung carcinogenesis. Further studies, both epidemiological and experimental, are needed to replicate the present findings and to clarify the mechanism(s) of sucrose intake in lung carcinogenesis.