Fever and shock are symptoms of acute disseminated candidiasis. Phagocytic activity of the reticuloendothelial system (RES), following a single administration of polysaccharide-protein complex, was studied with respect to the role of the RES in the pathophysiology of circulatory shock. The index of phagocytic activity was determined 15 or 120 minutes following IV administration of polysaccharide-protein complex (50 mg/kg) to mice, from the rates of clearance of carbon particles and of heterologous erythrocytes labeled with 51Cr. The mice were pretreated with hydrocortisone 300 mg/kg, methylprednisolone, 30 mg/kg, or saline 120 minutes before administration of the polysaccharide-protein complex. Depression of the phagocytic activity was observed following administration of polysaccharide-protein complex in both time intervals investigated. This depression could be prevented successfully by administration of both glucocorticoids studied. The fractional distribution of 86Rb was determined in other groups of identically treated mice. An increase of 86Rb uptake was found in the heart, lungs, and adrenals 15 minutes after administration of polysaccharide-protein complex. A decrease of 86Rb uptake was found in the intestines and spleen. These changes were also found in mice pretreated with glucocorticoids. A return to the normal picture of 86Rb fractional distribution was found 120 minutes after polysaccharide-protein administration. It was suggested that changes in phagocytic activity were not a result of altered hemodynamics.