Experimental data suggest that the recovery of renal function after ischemic or nephrotoxic acute renal failure is due to a replicative repair process dependent on predominantly paracrine release of growth factors. These growth factors promote renal proximal tubule cell proliferation and a differentiation phase dependent on the interaction between tubule cells and basement membrane. These insights identify the molecular basis of renal repair in ischemic and nephrotoxic acute renal failure and may lead to potential therapeutic modalities that accelerate renal repair and lessen the morbidity and mortality associated with these renal disease processes.