The alterations in single glomerular hemodynamics, glomerular size, and development of glomerular sclerosis after subtotal nephrectomy were assessed in approximately 32-d-old young and greater than 3-mo-old adult Munich-Wistar rats. In 6 wk, young rats developed more pronounced glomerular sclerosis and more marked elevation in blood urea nitrogen. The deep (versus superficial) cortical region of young rats was characterized by having a greater number of glomeruli with advanced sclerosis. Single nephron glomerular filtration rate of superficial glomeruli of the young increased to a much greater extent than whole kidney glomerular filtration rate, whereas there were comparable post-subtotal nephrectomy increases in whole kidney glomerular filtration rate in these two age groups, indicating that the deep glomeruli were exposed to a lesser hemodynamic load than were the superficial. Since the remnant nephrons of young and adult rats achieved equally high glomerular pressures and comparably large glomerular size shortly after subtotal nephrectomy, the unique susceptibility of young glomeruli to sclerosis is attributed to the intrinsic property of these glomeruli, rather than the abnormal hemodynamics or stimuli promoting hypertrophy and mesangial matrix accumulation imposed upon the glomeruli.