General pharmacological activities were examined with coumarin (A-1) and five kinds of coumarin derivatives, 4-methylcoumarin (A-3), 2-thiocoumarin (B-1), 6-aminocoumarin hydrochloride (E-2), 6-aminocoumarin coumarin-3-carboxylic acid salt (G-22), and 6-chlorocoumarin (J-2). Acute toxicity (LD50) by oral administration decreased in the order of G-22, A-1, J-2, E-2, B-1, and A-3, and the order of A-1 and J-2 was reveresed by subcutaneous injection. Of various central effects, antipyretic action was the strongest and some of them, notably A-3, B-1, E-2, and J-2, also showed hypnotic action but none of them showed any significant analgesic or antipmetic action. Majority of these compounds showed inhibitive action on the cardiovascularr system, as well as hypotensive and adrenolytic actions. G-22 had a comparatively strong hemolytic, anticoagulant, and erythrocytopenic actions. These compounds did not have any local anesthetic, mydriatic, spasmolytic, or antihistamine actions.