Oriental hornet (Vespa orientalis) venom sac extract (VSE) was topically applied to experimental wounds produced on the back skin of rats in order to observe histologically its effect on the healing process. In other studies the collagenolytic effect of VSE was investigated. The results clearly indicated that application of VSE enhanced the process of wound healing. Two weeks after wound induction a thick epidermis and maturation of the dermal connective tissue were seen in the experimental animals, whereas in the controls the dermis was thin and still showed granulation tissue, and the epidermis was thin. Incubation of VSE with purified neutral salt-soluble collagen (NSSC) labeled by reduction with [3H]NaBH4 brought about degradation of the substrate. It is assumed that VSE enhances the process of wound healing in the skin, probably due to its collagenolytic effect.