Protease and elastase from Pseudomonas aeruginosa were inoculated in female mice by intravenous, intraperitoneal, intrapleural and intranasal route, and the lethality and damage of various organs were examined. The protease and elastase exhibited respectively the following minimum lethal dose (MLD) values in 24 hr; 300 and 375 mug inoculated intravenously; 200 and 125-250 mug intraperitoneally; and 100 and 62.5 mug intrapleurally. The instillation of a defined dose of the enzyme by the intranasal route was difficult to control, therefore the MLD could not be defined exactly. The protease and elastase were capable of eliciting hemorrhage at various organs of mice according to the route of inoculation. Of protease, intravenous injections elicited petechial hemorrhage at the lungs and parietal bone-area, and severe one in the medullary area of kidney. The intraperitoneal injection resulted in petechial hemorrhage of the lungs, diaphragm, peritoneum and gastrointestinal serosa. Intrapleural injections and intranasal instillation resulted in confluent pulmonary hemorrhage. Of elastase, intravenous injections elicited confluent pulmonary hemorrhage, hemorrhage in the medullary area of kidney and cerebral ventricles, and petechial hemorrhage at the stomach-walls. The intraperitoneal injections resulted in petechial hemorrhage at the lungs, diaphragm, peritoneum and gastointestinal serosa. Intrapleural injections resulted in confluent pulmonary hemorrhage, and petechiae at the diaphragm and pleura. Intranasal instillation resulted in confluent pulmonary hemorrhage.