Disulfiram, 500 mg/day, raised serum cholesterol levels in alcoholic persons from a mean of 193 +/- 16.4 mg/dl to 227.2 +/- 17.2 mg/dl after 3 weeks and 264 +/- 40 mg/dl after 6 weeks. This increase was not seen in a group taking pyridoxine 50 mg/day in addition to disulfiram 500 mg/day. In contrast to the disulfiram and disulfiram-pyridoxine treatment groups, control groups receiving pyridoxine alone, or no drug, had a 33 mg/dl reduction in serum cholesterol during the first 3 weeks of abstinence, a finding consistent with other evidence showing a rapid decrease in serum lipids on abstinence from alcohol. Patients taking disulfiram 250 mg/day, with or without pyridoxine, did not have this expected decrease in serum cholesterol. Since increased serum cholesterol is one of the risk factors in a coronary heart disease, chronic disulfirm therapy may increase the incidence of arteriosclerotic cardiovascular disease, as has been the case with chronic exposure to carbon disulfide, a principal metabolite of disulfiram.