This prospective follow-up study of 422 19-yr-old subjects born very preterm in The Netherlands was performed to determine whether intrauterine growth retardation (IUGR) predisposes to abnormal GFR and microalbuminuria in adolescents. GFR (ml/min per 1.73 m2) was estimated using the Cockcroft-Gault equation, and albumin-creatinine ratio (mg/mmol) was calculated in a cohort of 19-yr-old subjects born very preterm (gestational age <32 wk) in 1983. Birth weights were adjusted for gestational age and expressed as standard deviation scores (sds) as a measure of IUGR. All subjects had normal renal function. Birth weight (sds) was associated negatively with serum creatinine concentration (μmol/L) (β = -1.0 μmol/L, 95% confidence interval [CI]: -1.9 to -0.2), positively with GFR (β = 3.0, 95% CI: 1.7 to 4.2), and negatively with the logarithm of albumin-creatinine ratio (β = -0.05, 95% CI: -0.09 to -0.01) in young adults born very preterm. IUGR is associated with unfavorable renal functions at young adult age in subjects born very premature. These data suggest that intrauterine growth-retarded subjects born very premature have an increased risk to develop progressive renal failure in later life. Copyright © 2005 by the American Society of Nephrology.