In a prospective case-control lung cancer study in the west of Sweden, the relationship between lung cancer, smoking and dietary factors was investigated. Suspected cases were collected from pulmonary units at two central hospitals in the area investigated and population controls of the same age and sex were selected from registers. The majority of cases and controls were interviewed by specially trained nurses, using a food frequency questionnaire. The lung cancer diagnosis (ICD 7, 162.1) was made using data from the local cancer register. In an analysis based on 308 cases and 504 controls, a dose-related increase in lung cancer risk for smokers was found, although no significant risk was found for males smoking 1-10 cigarettes/day for less than 20 years. A lower consumption of vegetables was related to a higher risk, both for smokers and nonsmokers. A higher consumption of milk was related to an increased risk.