Hypertension has been shown to be closely associated with metabolic disorders such as diabetes mellitus and gout. The aim of this study was to establish the incidence of both these diseases in hypertensive patients and their age-matched controls and to assess the risk associated with diuretic treatment. The results refer to the data base of 2295 hypertensive and 2280 controls from the General Practice Hypertension Study Group who were screened for hypertension. The rescreened hypertensive subjects (n = 1190) and their controls (n = 938) were followed for an average of 8 years. The diagnosis of diabetes and gout was made by their general practitioners. After 8 years of follow-up, diabetes mellitus was diagnosed in 5.0% of hypertensive and 1.5% normotensive subjects. The diagnosis of gout was made in 3.1% and 0.9%, respectively. Moreover, diabetes mellitus occurred more frequently in both hypertensive men and women, with diuretic treatment and without (respectively, men given diuretic: relative risk (RR) = 2.74, 95% confidence interval (CI): 0.99, 7.5; and men not given diuretic: RR = 2.25, 95% CI: 1.0, 5.3: women RR = 4.03 95% CI: 1.5, 10.8, and RR = 3.47, 95% CI: 1.4, 8.9) in comparison with their age-matched controls. For gout the excess was confirmed in hypertensive men with and without diuretic treatment (RR = 6.25 (95% CI: 2.4, 16.7) vs 3.93 (95% CI: 1.6, 9.7)).