A long-term clinicomorphological study in 227 patients with acute renal failure due to intrinsic renal damage shows the clinical value of renal biopsy for assessing treatment and predicting prognosis. Early morphological diagnosis enables appropriate therapeutic measures, which play their part in patient survival and renal survival. Present long-term results show that 5 years after the acute episode, chronic renal failure may be expected to occur in about 50% of cases with acute renal failure due to glomerular and vascular injuries. Tubulointerstitial lesions are associated with definitely better long-term prognosis.