Apolipoprotein B levels were studied in relation to cigarette smoking, coffee and alcohol consumption, physical activity, age and body mass index in 253 men aged 21-61 years. The mean apolipoprotein B level was 7.3 +/- 3.2 mg/dl and was higher for smokers compared with non-smokers. Considering the smokers of over 20 cigarettes/day and the non-smokers, this difference reached 12.6 +/- 4.3 mg/dl. A significant increase of 7.2 +/- 3.5 mg/dl in apolipoprotein B levels was observed in the subjects who drank over 3 cups of coffee/day compared with the remaining subjects, but the increase was only 4.3 +/- 3.7 mg/dl when we made a correction for cigarette consumption. Furthermore, for cigarette smoking and coffee consumption, there is apparently an interactive effect with BMI and/or age (vs apolipoprotein B levels). However, with a stepwise selection among explicative variables [age, BMI, smoking (yes/no) and coffee consumption (less than or equal to 3, greater than 3 cups/day)] and all their interactions of first order, only the interaction between BMI and smoking (BMI*smoking: b +/- ES (b) = 0.3029 +/- 0.0303), and age and BMI (age*BMI), are significantly and positively related to serum levels of apolipoprotein B. Thus cigarette smoking, interacting with high BMI, appear related to higher apolipoprotein B levels.