A local Shwartzman response was elicited in rabbits by an intradermal injection of the Salmonella typhosa endotoxin lipopolysaccharide (LPS) followed 24 hours later by an intravenous challenge injection with zymosan. After the intravenous challenge, necrotizing vasculitis developed in the prepared skin sites which was characterized by microthrombi, accumulation of neutrophil granulocytes, fibrin deposition and extravasation of red blood cells. Evans' blue extravasation into the altered tissue was significantly reduced, and histologically, the intensity of the Shwartzman reaction in the skin was reduced by pretreatment with thalidomide and dexamethasone. The mechanism of reduction of an LPS-induced local Shwartzman reaction by thalidomide is discussed.