The Brenner hypothesis postulated that low birth weight and decreased nephron number at birth are linked to chronic kidney disease and systemic hypertension in adulthood. To date, little is known about the effect of extrauterine growth retardation (EUGR) on adult kidney disease. Bacchetta et al. present novel data using inulin to show a decrease in renal function for premature children with EUGR. The role of protein nutrition and timing in nephrogenesis is discussed.