We prospectively analyzed 70 consecutive patients who developed acute renal failure (ARF) in the intensive care unit (ICU) during a six year period to define prognostic factors and outcome. Age, sex, preexisting chronic diseases, systemic infections, number of organs failing during the disease course, need and mode of renal replacement therapy (RRT), and length of stay in ICU were recorded. Analysis of factors in survivors (n=7, Gp A) and nonsurvivors (n=63, Gp B) was done by univariate and multivariate analysis. The mean age of patients was 28.6 years. Forty nine (70%) patients developed ARF following surgery, whereas 21 (30%) developed ARF in a medical setting. Cardiovascular surgery (39) and pancreatic surgery (7) were important causes in the surgical group, whereas in the medical group acute pancreatitis (11) was the main causative factor. One patient had ARF only, while in the rest, other organs were also involved. In more than 80% of these patients, organ failure and sepsis were present before the onset of ARF. Fifty two (74.3%) patients required dialytic support. The overall mortality was 90%. Number of organs failing, (1.5 +/-9 in Gp A vs 3.6 +/- 8 in Gp B), presence of systemic infection (1 in Gp A vs 55 in Gp B), prolonged stay in ICU (3.7 +/- 1.1 days in Gp A vs 8.0 +/- 5.4 in Gp B) and need for RRT (2 in Gp A vs 50 in Gp B) correlated with the mortality. Using multiple logistic regression analysis, only multiple organ failure (3 or more) correlated with the mortality. We conclude that multiple organ failure is a poor prognostic factor in patients with ARF in the setting of the ICU.