The effect of arterial hypertension on the progression of chronic renal failure (CRF) was evaluated in 108 patients who eventually required dialysis in the 8 year period of the study. Patients' average serum creatinine (SCr) concentration at first examination was 239.7 +/- 45.3 mumol/liter and at the start of dialysis was 1,661.0 +/- 181.9 mumol/liter. The mean duration of pre-dialysis follow-up was 53.7 +/- 15.7 months. The mean monthly increase in SCr was 18.8 +/- 13.4 and 2.1 +/- 1.4 mumol/liter/month in hypertensive and normotensive CRF patients, respectively (P < 0.001). The CRF patients with a diastolic blood pressure (BP) < 89 mm Hg had a significantly (P < 0.05) slower rate of decline in renal function than the patients with a diastolic BP > or = 90 mm Hg. There was a significant relationship between a mean diastolic BP > or = 90 mm Hg and the rate of monthly increase in SCr (r = 0.81, P < 0.001). These data indicate that control of diastolic BP in CRF patients is a potentially effective way to slow the rate of decline in renal function.