General pharmacological properties of urinary trypsin inhibitor (UTI) following intravenous administration of 1,000,000 units/kg were examined in terms of effects on central nervous system, cardiovascular system, respiratory system, gastrointestinal system in mice, rats and rabbits. Administration of UTI (1,000,000 units/kg, iv) had no effect on central nervous system; no influences on pentobarbital sleeping time, spontaneous activity, normal body temperature, chemoshock produced by pentylenetetrazole solution, writhing syndromes induced by 0.6% acetic acid solution, and motor coordination of mice. The administration of UTI (1,000,000) units/kg, iv) in rats had no effect on systolic blood pressure and pulse rate. UTI (500,000 units/kg, iv) given to anesthetized rabbits showed no effect on respiratory rate. However, it showed significant elevation of respiratory rate at the concentration of 1,000,000 units/kg. Gastric secretion of rat and intestinal motility of mice were not influenced by the dose of 1,000,000 units/kg. In terms of autonomic nervous system, the material did not show direct effect and inhibitory or augmentative action of histamine- or acetylcholine-induced contraction at the concentration of 2,000 units/ml in the isolated ileum of guinea pig.