It has been suggested that impaired fetal kidney development may contribute to the onset of hypertension. This study was designed to investigate the outcome of adult subjects who were born preterm or growth retarded. Subjects(mean age± SEM 26±1 years, n=34) were randomly selected from the neonatal clinical records. They were allocated in 3 groups: born full term with approporiate birth weight, born full term with birth weight < 2800 g, or born before gestational week 32. Blood pressure was recorded during 24 hours. Renal volume was determined by ultrasound. GFR and ERPF were determined by the clearance of inulin and PAH. U-albumin excretion rate and plasma insulin, IGF-1, IGFBP-1, cholesterol, HDL, LDL and triglycerides were also determined. A positive correlation was found between birth weight and adult renal volume (r = 0.35, p<0.04). Subjects with birth weight < median had higher systolic blood pressure (129±3 vs 121±2 mmHg) and lower GFR (101±2 vs 108±3 ml/min/1.73mBSA) and renal volume(128±4 vs 139±5 cm2 BSA) than subjects with birth weight> median. Gestational age was positively correlated to adult ERPF (r = 0.35, p<0.04). Subjects born preterm had lower GFR (101±2 vs 108±3), ERPF (641±26 vs 719±23 ml/min/1.73mBSA) and kidney volume (128±4 vs 140±5) than subjects born full term. Adult kidney volume was positively correlated to GFR (r = 0.44, p<0.01) and ERPF (r = 0.55, p<0.001). Subjects with renal volume < median had a significantly higher systolic pressure (123±2 vs 116±1) and lower ERPF (636±22 vs 719±27) than those with renal volume > median. All pathological 24-hours pressure profiles were in the group with renal volume < median. IGF-1 was lowest in the adults born full term but with low birth weights (207±73) and highest in the adults born preterm(258±40) (control adults: 231±21). No correlation was found between gestational age, birth weight or kidney volume with other variables. In conclusion, this study shows a weak but significant correlation between fetal growth retardation and renal function in adulthood. Adult renal volume and GFR are lower in adults who were born prematurely or small for age. Small renal volume in adulthood may be associated to the early onset of hypertension.