In the present study the prevalence of obesity and its association with ischemic heart disease, recognized according to clinical criteria (chest pain or previous infarction) and/or instrumental data, were described in 8,847 normotensive subjects and in 867 hypertensive subjects, hospitalized during a ten years period (1983-1992), through a cross-sectional study. In view of this all the subjects were considered as lean or obese according to their body mass index (BMI) and to sex specific cut-off values reported in the Italian Consensus Conference on Obesity. In particular, according to BMI values, the subjects were grouped as lean, overweight, moderate and severe obese subjects. Our results indicated that 3,982 normotensive subjects (45%) could be considered lean, whereas 2,654 of them (30%) were overweight, 1,769 of them (20%) were moderate obese and 442 of them (5%) were severe obese. On the contrary only 206 hypertensives (23.7%) might be considered lean, whereas 313 (36.1%) were overweight, 302 (34.8%) were moderate obese and 46 (5.3%) were severe obese. According to age subgrouping (lower than or equal to 65 years or higher than 65 years) the distribution of hypertensives within the lean, overweight, moderate and severe obese groups did not change significantly, but, according to sex subgrouping, the distribution of hypertensives within the BMI groups was significantly different (chi 2, p < 0.001). When we considered the degree of hypertension, distribution of hypertensives was significantly different according to c2 test (p < 0.004), suggesting that the percentage of the subjects with severe hypertension increased only in subjects with severe obesity. Concomitant ischaemic heart disease (IHD) was also documented in 350 normotensives (4%) and in 119 hypertensives (13.8%). The prevalence of IHD was not significantly different in lean, overweight, moderate and severe obese hypertensives, also when sex and smoking habits were considered. Our data indicated a strong association between obesity and hypertension. In addition they may be consistent with the suggestion that obese hypertensives were not characterized by a lower risk of ischaemic heart disease (IHD), than lean hypertensives.