A group of 317 overweight men and 565 overweight women was compared with an age-matched normal control group of 444 men and 627 women in order to establish whether hypertension was more often recorded in the obese group. This was done by analysing the continuous morbidity registration of four general practices with a follow-up of up to 17 years. The risk of hypertension was found to be three to four times higher in overweight persons than in those of normal weight, and in women a linear relationship was found between the degree of overweight and the incidence of hypertension. The fat distribution was studied in 292 overweight persons, and fat deposited predominantly in the abdominal region was found to be related to the prevalence of hypertension, particularly in subjects under 50 years of age. Along with the degree of overweight, therefore, the fat distribution might be a useful aid in the early detection of hypertension. Since it is difficult to achieve long-term success in the treatment of overweight, its prevention merits special attention in general practice.