The effects on blood pressure (BP), renal function, and urinary albumin excretion (UAE) of 14 years of antihypertensive treatment were studied and compared to the changes seen with normal aging. The studied groups included randomly selected men with newly diagnosed primary hypertension at baseline (n = 23) and normotensive (NT) men of the same age (n = 11). The hypertensives (HT) were treated with beta-blockers either as monotherapy or combined with diuretics or hydralazine. Glomerular filtration rate (GFR; inulin clearance), renal blood flow (RBF, para-aminohippurate clearance), renal vascular resistance (RVR), and 24-h UAE were determined. The two groups were investigated at baseline (before treatment) and after 7 and 14 years. At baseline, BP and RVR were significantly increased and RBF was significantly decreased in the HT over that in the NT. The BP in the HT was significantly reduced after 7 years of treatment and a further but nonsignificant reduction to 139 +/- 14/88 +/- 6 mm Hg (mean +/- SD) was seen after 14 years. GFR in the HT was significantly reduced from 103 +/- 15 mL/min to 84 +/- 19 mL/min (mean +/- SD) after 7 years, but no further reduction was seen after 14 years. During the 14 years RBF decreased and RVR increased in the HT but these changes were of the same magnitude as in the NT. The UAE did not change significantly during the study. In conclusion, good blood pressure control with conventional antihypertensive treatment in mild to moderate primary hypertension seems to protect the kidney from progressive decline in GFR and increase in UAE. The increase in RVR and the decrease in RBF seen during 14 years of antihypertensive treatment was of the same magnitude as that seen with normal aging.