The relationship between obesity, both general obesity (BMI) and central obesity (measured by the ratio of iliac and thigh circumferences), and a behavioural pattern, which includes alcohol consumption, smoking, stress and lack of sporting activity, was investigated in 467 middle-aged French working men. BMI and central obesity were closely correlated (r = 0.34). Alcohol consumption was positively associated with central obesity (P < 0.001) but it did not significantly influence BMI. BMI decreased with cigarette smoking (P < 0.001), but central obesity only increased significantly after adjustment for BMI (P < 0.05); thus for a given BMI, smoking was associated with a greater degree of central adiposity. Resting heart rate (considered as a measure of stress) was positively associated with both BMI and the iliac-thigh ratio (P < 0.01, P < 0.05), the latter association being due to general obesity. Sporting activity and BMI were only marginally associated (P < 0.07) but central obesity decreased with activity (P < 0.01). Jointly, alcohol consumption, cigarette smoking, the resting heart rate and sporting activity explained 8% of the variance in the iliac-thigh ratio; after adjustment for BMI these behavioural variables still explained 6% of the variance. Central adiposity, which has recently been described as a risk factor for coronary heart disease, non-insulin dependent diabetes and hypertension, was significantly associated with a potentially modifiable behavioural pattern.