It is well known that about three-quarters of a lightning discharge to the ground consists of multi-stroke flashes among which 3- or 4-stroke flashes are the most frequent. A new type of impulse-generator was developed which can produce 3-successive impulse voltages to simulate multi-stroke lightning flashes. Experiments were conducted to investigate the effects of multi-stroke flash on the living body and the results were compared with those for the well-known effects of a single-stroke discharge. The results demonstrated that in the case of the multi-stroke discharge, the animal died when of the energy of one of the individual impulses reached the lethal threshold value established for a single-stroke discharge. It was found that the effect of the individual impulses did not last longer than the stroke interval and did not exert an additive effect on the living body. In natural lightning discharges, the multi-stroke flash should be regarded as more dangerous than the single-stroke flash, since it is liable to an energy that exceeds the lethal threshold value and to be associated with a higher probability of a continuing current (known to be the most fatal of discharge components).