Prevalence of hypertension and relation of hypertension to renal function, type of glomerulonephritis or histological features were evaluated in 311 patients with idiopathic chronic glomerulonephritis. The overall prevalence of hypertension was 49.8%. At least in women, prevalence of hypertension was increased even at serum creatinine levels less than 1.1 mg dl-1 compared with the local general population. Prevalence of hypertension was 2.12 and 8.6 fold higher at serum creatinine 1.1-1.4 mg dl-1 in males and females respectively. In patients with untreated hypertension, a relation was found between mean blood pressure and subsequent decline of estimated GFR. Furthermore, in patients with arterial sclerosis, but not in patients without, a significant relation was found between blood pressure and subsequent increase in serum creatinine.