Previously, we reported the structural requirements of the cinnamic acid relatives for inhibition of snake venom hemorrhagic action. In the present study, we examined the effect of benzenepolycarboxylic acids and substituted benzoic acids against Protobothropsflavoviridis venom-induced hemorrhage. Pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid) was found to be a potent inhibitor of hemorrhage, with an IC(50) value of 0.035 μM. In addition, most of the antihemorrhagic activity of compounds tested in this experiment showed good correlation to acidity.