Large epidemiological studies suggest a clear relation between low birth weight and adverse renal outcomes evident as early as during childhood. Such adverse outcomes may include glomerular disease, hypertension, and renal failure. Data from autopsy material and from experimental models suggest that reduction in nephron number via diminished nephrogenesis may be a major mechanism, and factors that lead to this reduction are incompletely elucidated. Other mechanisms appear to be renal (e.g., via the intrarenal renin-angiotensin-aldosterone system) and nonrenal (e.g. changes in endothelial function). It also appears likely that the outcomes of fetal programming may be influenced postnatally, for example, by the amount of nutrients given at critical times.