Some derivatives of aminobenzoic acid were examined for their inhibitory activity against immune hemolysis and heat-induced hemolysis. Of the compounds tested, bis(salicylamido)benzoic acids were proved to have a potent inhibitory effect on both hemolytic reactions. In immune hemolysis, inhibitory activity of 2, 4- and 2, 5-bis(salicylamido)benzoic acid was a little weaker than that of sodium copper-chlorophyllin, but stronger than that of sodium citrate, dipotassium ethylenediaminetetraacetate, and non-steroidal anti-inflammatory drugs used as active controls. In heat-induced hemolysis, 2, 4-, 3, 5-, and 2, 5-bis(salicylamido)benzoic acid inhibited hemolytic reactions more pronouncedly than non-steroidal anti-inflammatory drugs. Structure-activity relationships and possible use of these active compounds as new drugs were discussed.