To examine whether dietary fat and cholesterol modifies lung cancer risk, a case-control study was conducted in Uruguay of 426 men diagnosed from1993 to 1996 with lung cancer, and 419 hospitalized frequency-matched controls. Dietary patterns were assessed using a 64-item food frequency questionnaire, which allowed the calculation of total energy intake. After adjustment for potential confounders through a model which included tobacco smoking, total energy, a term for all vegetables and fruits, and a-carotene in take, an increase in risk for total fat intake for all cell types of lung cancer was observed. Adenocarcinoma of the lung was associated strongly with saturated fat intake (odds ratio [OR] = 2.3, 95 percent confidence interval[CI] = 1.2-4.4), whereas small-cell lung cancer was associated with dietary cholesterol (OR = 2.8, CI = 1.1-7.5). These results suggest that the association of saturated fat and cholesterol could be type-specific, but the high correlation existing between dietary lipids precludes any strong statement about this point.