The protein toxin staphylococcal enterotoxin B (SEB) produces a clinical syndrome somewhat similar to that of gram-negative endotoxins. Our studies indicate a further similarity to endotoxin in that SEB is rapidly cleared from the plasma of monkeys. However, data reported herein show that an effective Thorotrast blockade of the reticuloendothelial system (RES) does not produce a significant change in the rapid disappearance kinetics of SEB. This observation contrasts with what is known regarding endotoxin clearance. Furthermore, other data reported herein indicate that acute bilateral renal artery ligation produces a profound delay in SEB clearance from plasma. A possible mechanism for renal degradation of SEB is theorized. The RES may play a less important role in the clearance of SEB. This finding contrasts with the demonstrated importance of the RES in clearance and detoxification of gram-negative endotoxin.