The reticuloendothelial system phagocytic activity, estimated by the plasma elimination rate constant of 99mtechnetium-sulfur colloid, was studied in 41 decompensated cirrhotics and 10 normal subjects. The results were related to the incidence and type of bacterial infections occurring during hospitalization and follow-up, and to survival. The elimination rate constant of 99mtechnetium-sulfur colloid was lower in cirrhotic patients (0.168 +/- 0.007) (means +/- S.E.) than in normal subjects (0.220 +/- 0.005) (p less than 0.01). Cirrhotics were divided into two groups. Group I (16 patients) and Group II (25 patients) had normal or reduced elimination rate constant of 99mtechnetium-sulfur colloid, respectively. Both groups were similar in relation to clinical and biochemical data, hepatic blood flow, and wedged hepatic venous pressure. However, the liver scan and the elimination rate constant of indocyanine green were more altered in Group II. Patients in Group II developed acute bacterial infections more frequently than did patients in Group I. During hospitalization (24 +/- 2 days), bacteremia occurred in six patients in Group II and in none in Group I (p less than 0.05). During follow-up (28 +/- 3 months), 5 patients in Group II and none in Group I developed bacteremia (p less than 0.05). The cumulative survival rate of Group I patients was higher (p less than 0.05) than that of Group II patients at 3 months (100 vs. 80%), 6 months (94 vs. 68%), 24 months (74 vs. 42%), and 48 months (68 vs. 34%). We suggest that decompensated cirrhotics with depressed reticuloendothelial system phagocytic activity are at great risk to acquire bacteremia, and that reticuloendothelial system phagocytic activity has prognostic value in cirrhosis.