Cardiovascular risk factors were studied from 1985 to 1987 in population samples in two French regions with different ischaemic heart disease mortality rates in Bas-Rhin (Strasbourg MONICA centre) and in Haute-Garonne (Toulouse MONICA centre). These rates were, among men, 109/100,000 in Bas-Rhin, and 72/100,000 in Haute-Garonne. 1,253 and 1,319 men and women aged 35-64 participated in the survey. In each region, identical investigation methodology was used, according to MONICA protocol. The average weight in both sexes was higher in Bas-Rhin than in Haute-Garonne (5 Kg more for men and 6 Kg more for women). After adjustment for age, body mass index and tobacco consumption, arterial systolic blood pressure was higher for men in Bas-Rhin (145 mm Hg) than in Haute-Garonne (133 mm Hg). Similar differences were observed in women. Higher proportions of hypertensive participants of both sexes and in all age groups were registered in Bas-Rhin than in Haute-Garonne. The number of smokers and the amount of tobacco consumption did not differ between the two centres. Mean serum cholesterol was higher in Haute Garonne (5.95 mmol/L for men and 5.88 mmol/L for women) than in Bas-Rhin (5.57 mmol/L for men and 5.51 mmol/L for women). Also high-density lipoprotein (HDL)-cholesterol values were higher in Haute-Garonne, and can partly explain the regional difference in total cholesterol.