Data on the association between alcohol abuse and cancer morbidity are scarce in large cohorts of non-hospitalized alcoholic men an women. Of 18,368 alcohol abusers who entered an out-patient clinic in Copenhagen between 1954-1987, 18,307 were followed. Their cancer incidence was compared to that of the total Danish population. The overall morbidity of cancer was significantly increased among alcohol abusers. The men developed 1441 cancer cases (RR = 1.6), and the women 182 cases (RR = 1.5). Significantly increased incidences were found for cancer of the tongue, mouth, pharynx, oesophagus, liver, larynx, lung, pleura, and secondary cancer. The women had a significantly increased risk of cervical cancer (RR = 2.0). The men developed prostatic cancer significantly more frequently than expected (RR = 1.4). The relative risks of cancer of the stomach, pancreas, kidney and endocrine system were only slightly increased. The risk of breast cancer in women was not significantly increased (RR = 1.3).