The relationship between diet and alcohol and lung cancer was evaluated among participants of the New York State Cohort (United States), comprising 27,544 men (395 cases) and 20,456 women (130 cases) who completed a brief mailed questionnaire in 1980. Participants were followed up through 1987 with the assistance of the New York State Department of Health's Vital Statistics Section and Cancer Registry. Among men, inverse relationships with vitamin C, folate, and carotenoids, and positive associations with total fat, monounsaturated and saturated fat were observed after adjusting for age, education, cigarettes/day, years smoking, and total energy intake. The relationships observed with folate and saturated fat were stronger for heavy smokers. Also, the effect of folate, total fat, and monounsaturated fat seemed to be limited to squamous cell carcinomas. We found no indication that cholesterol or polyunsaturated fat was associated with lung cancer. Diet did not appear to exert a major role on lung cancer risk among women. Although diet modification should never be considered a substitute for smoking cessation, its role as an additional strategy in lung cancer prevention deserves attention.