We report two cases of envenomation by a Madagascan opisthoglyphous snake, Ithycyphus miniatus. In both cases, the snake bit the finger of a human who was preparing an experiment by tying a string around the snake body. Symptoms of the first case included temporal severe local pain and extensive bleeding. In the second case, severe pain accompanying obvious local swelling was caused and lasted for several hours. The present observations indicate that bite by I. miniatus potentially causes serious physiological effects in humans although the snake is basically calm and reluctant to bite.