Objectives: To evaluate the Individual Severity Score (ISS) as a predictor of mortality in patients with acute renal failure (ARF) and to determine mortality associated factors. Methods: Clinical records of patients with de diagnosis of ARF at the Hospital Arzobispo Loayza (HAL) of Lima (Peru) between the years 1995 and 2000 revised. The optimal cut point for sensitivity and specificity of the ISS was assessed using ROC curve analysis. Results: 128 clinical records of patients with ARF were revised. The mortality rate was 10.94 % (T4/128). Patients who died were significatively older and showed more frequently hypotension, jaundice, need of mechanical ventilation and coma. The optimal cut point for the ISS was 0.74 (sensitivity of 71% and specificity of 100%). The area under the curve value was 0.91 (CI95 0.81-1.03). Conclusion: The ISS was shown to be a cheap, easy clinical tool with an elevated discriminant ability in the study population. Mortality associated factors were similar as previously reported.