During a five year period, 28 episodes of spontaneous bacterial peritonitis were documented. The number of cases recognized annually increased during the study period. Clinical and laboratory features of spontaneous bacterial peritonitis were similar to those previously reported; however, mortality was considerably lower (57 per cent). Factors associated with adverse prognosis were increasing hepatic encephalopathy, more than 85 per cent granulocytes in peripheral blood or ascitic fluid, total bilirubin greater than 8 mg/dl and serum albumin less than 2.5 g/dl. Temperature greater than 38 degrees C was associated with increased survival. Infection by enteric organisms was associated with higher mortality than infection by nonenteric organisms. Unexpectedly, patients with bacteremia fared no worse than those whose blood remained sterile. The data suggest that in patients with leukocyte counts greater than 1,000 cells/mm3 and more than 85 per cent granulocytes in their ascitic fluid, the likelihood of spontaneous bacterial peritonitis is high. Such patients deserve empiric antibiotic therapy pending the results of appropriate cultures.