Background. Hypertension is reported to be one of the most common causes of end-stage renal disease (ESRD) in Europe and in the United States. However, the frequency with which treated primary hypertension leads to renal failure is not known. The majority of patients with ESRD have hypertension. Whether this is the cause or the consequence of the impaired renal function is often not possible to establish. Methods. To determine if treated primary hypertension can lead to ESRD, we studied the development of serum creatinine levels in 686 white hypertensive men, recruited from a random third of the male population aged 47-55 years living in Goteborg, Sweden (n = 9998; 7495 participants). At entry and during 20 years follow-up, all signs of kidney disease, secondary hypertension, or increase in blood pressure were investigated. Records of patients with a serum creatinine value greater than or equal to 130 mu mol/l at any time during the observation period were thoroughly studied to ascertain the cause of the impaired renal function. Results. A serum creatinine level above 130 mu mol was seen in 8.9% (61/686) of the treated hypertensives during the 20 years of follow-up. An underlying renal disorder was found in 7.2% (49/686) of the patients; renoparenchymal disease (2.2%), renovascular disease (1.5%), diabetic nephropathy (1.2%) or a urological disease (1.6%). Only 1.7% ( 12/686) of the hypertensives showed a moderate progressive increase in serum creatinine of unknown cause. The serum creatinine in this group was 133 +/- 8 mu mol/l (mean +/- SD; range 124-144) after 15 years and 139 +/- 7 mu mol/l (range 132-151) after 20 years. Thus, none of these patients aged 66-71 years had developed ESRD or a clinically important reduction in renal function. Conclusion. The main finding in this population-based study of white middle-aged men with primary nonmalignant hypertension was that long-term antihypertensive treatment was not associated with development of end-stage renal disease or even an abnormal progressive decline in kidney function.