A total of 993 mice, rats, guinea pigs, and rabbits were exposed to sharp-rising overpressures of various short durations. They were mounted on a concrete pad above which high-explosive charges, ranging in weight from 0.50 oz to 64 lbs, were detonated. Pressure-time measurements were obtained with pencil- type and shock-tube piezo-electric gauges on the pad directly beneath the charges. The duration of the blast waves ranged from 0.40 to 6.8 msec. The LD/sub 50/ pressures were calculated for each species at the different pulse durations. In general, the pressures required to produce 50% lethality rose at the shorter durations. Combining the results of this study with those from previous shock- tube investigations made it possible to define the tolerance of four small-animal species to sharply rising overpressures as a function of pulse duration. (auth)