Objective: To see if it is possible to predict mortality in isolated post-traumatic acute renal failure. Design: Retrospective study 1984-1990 inclusive. Setting: Teaching hospital, South Africa. Subjects: Thirty-nine patients who developed isolated post-traumatic acute renal failure out of 106526 admissions for trauma. Interventions: Standard aggressive management of traumatic injury and acute renal failure. Main Outcome Measure: Death. Results: Fifteen of the 39 patients who developed post-traumatic acute renal failure died (39%). Blunt trauma from assaults was a major cause of acute renal failure (16/39, 41%). Hypotension and hyperkalaemia were the two main predictors of death having a mortality of 63% and 52%, respectively. Conclusion: Clinicians should be aware of the risks of hypotension and hyperkalaemia in injured patients. Preventive measures such as aggressive resuscitation and timely correction of serum electrolyte concentrations are essential in such patients.