The separate and joint effects of cigarette smoking and alcohol consumption on serum concentrations of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides were investigated in 46 750 men attending the BUPA Health Screening Centre in London during the period 1983-1987, after allowing for differences in age, body mass index and exercise level. Drinking alcohol was found to raise both total cholesterol and HDL-C concentrations, in such a way that HDL-C as a percentage of total cholesterol increased with increasing alcohol consumption. LDL-C concentrations increased with increasing alcohol consumption in non-smokers, but decreased in those smoking over 10 cigarettes per day. Drinking had no significant effect on triglycerides except at high levels of consumption. Smoking raised total cholesterol, LDL-C and triglycerides, but lowered HDL-C concentrations. In particular, smoking even small amounts could negate any protective benefit in HDL-C concentrations gained from moderate consumption of alcohol. Assuming a desirable lipid profile to consist of low total cholesterol, LDL-C and triglycerides and a high HDL-C value, this is best achieved for men by being a non-smoking moderate drinker.