In 24 young normotensive subjects (mean age 22.25 +/- 5.65 years) with one hypertensive parent (FH(+)-), 22 subjects (mean age 23.55 +/- 5.17 years) with two hypertensive parents (FH+ +/-), and a control group of 16 age and gender matched subjects (mean age 22.50 +/- 6.00 years) with two normotensive parents (FH--), creatinine clearances and microalbuminuria (MA) were measured. Blood pressure was monitored for 24 hours and mean arterial pressure (MAP) was calculated and compared between groups. No significant differences were recorded. FH(+)- and FH++ subjects had significantly higher MAP over the sleeping period than FH-- subjects (78.63 +/- 1.71, 78.95 +/- 1.27; and 72.91 +/- 1.35 mmHg respectively; p < 0.02). Creatinine clearance was higher in FH(+)- and FH++ group compared to FH-- subjects (2.39 +/- 0.17; 2.29 +/- 0.17; and 1.66 +/- 0.11 ml/sec respectively; p < 0.01). Hyperfiltration correlated with MAP in FH++ subjects (2.29 +/- 0.17 ml/sec; 92.45 +/- 7.39 mmHg; r = 0.52 i p < 0.03). MA correlated neither with creatinine clearance nor with MAP. Our results suggest that hypertension may develop as a consequence of the long-lasting, higher GFR, which may accelerate the age-related process of sclerosis both in the small arterioles and the glomeruli.