In the Basel study (BS) (1960-73) on cardiovascular and peripheral arterial diseases, a mortality follow-up was completed for the period 1965-80. Of the 4,224 men at risk for these diseases, 531 died. The causes of death were established from the death certificates and classified into 8 groups. For each case 2 age- and sex-matched controls were selected and compared with the corresponding cases with regard to the various variables obtained at the three examinations (1960, 1965, 1971). This report dealth with cancer mortality, plasma lipids, plasma vitamins, alcohol and cigarette consumption, and intake of milk and citrus fruits. The results were all obtained at the second follow-up examination (BS III, 1971-73). Cancer of the lung, stomach, large bowel, and all other sites were treated separately. The average follow-up from BS III until death varied from 3.7 years (other sites) to 4.9 years (cancer of the lung). Of 129 cancer deaths, the highest incidence was found for cancer of the lung (38) followed by stomach (19) and large bowel, (15) and the remainder (57) was for other sites. Plasma lipids did not differ significantly among cases and controls. However, the lowest values were observed in colorectal cancer and gastric carcinoma (mean cholesterol, 213 mg/dl). beta-Carotene was significantly lower in cancer cases of the lung than in controls (14.8 micrograms/dl vs. 23.7; P less than .05). It was also low in gastric cancer cases (13.0 micrograms/dl). Vitamin A was below average only in cases with gastric cancer (difference due to the small number not significant). Vitamin C was consistently lower in cancer cases than in controls. The lowest value was found for cancer of the stomach and corresponded to a below-average consumption of citrus fruits. Vitamin E was low in cancer of the colon. Plasma lipids correlated strongly with vitamin E (tau = 0.5) and to a lesser extent with vitamin A (tau = 0.25). beta-Carotene correlated poorly with beta-lipoproteins (low-density and very low-density lipoproteins) but significantly with total cholesterol. Smoking was inversely related, as was alcohol consumption, to the beta-carotene level. From these results, the conclusion was that vitamins influence carcinogenesis in humans.