A series of four swim experiments using a 20 deg C water bath was conducted with female, albino rats, Sprague Dawley strain. The purpose of the study was to: (1) investigate the effects of exhaustive exercise on rats at various times after exposure to airblast, (2) determine a time when exercise ceases to influence the mortality of blast-injured animals, and (3) estimate the recovery time required after blast trauma before maximum or near-maximal exercise capability is restored. It was found that rats which were forced to swim to exhaustion as late as 1 hour following exposure exhibited a fourfold increase in lethality over nonexercised rats exposed to the same blast levels, and that exercise continued to exert an influence on blast lethality at 4 hours following exposure. However, the added stress of swimming did not increase lethality at 24 hours or 7 days. In addition, a near-normal swim performance was apparent at 7 days after traumatization.