Relationships between coffee drinking and cancer incidence were examined in a 10-year complete follow-up of 21,735 men and 21,238 women aged 35-54 years. The study population participated in a cardiovascular screening in three countries in Norway during 1977-82. Data on coffee and smoking habits were based on information from a self-administered questionnaire. There was no association between coffee consumption and overall risk of cancer. A positive association was found between coffee drinking and risk of lung cancer, also after adjustment for age, cigarette smoking, and county of residence. Residual confounding by cigarette smoking and other lifestyle factors cannot be ruled out. A negative association was found with cancer of buccal cavity and pharynx and with malignant melanoma in women. No significant associations were found between coffee drinking and incidence of cancer of the pancreas or the bladder.