Because of the scarring and limited motion that occur as the final result of edema of the hand, prevention or decrease of the original edema would be desirable. Clinically, in patients with postoperative edema of the hand, we feel that aqueous chymotrypsin aids in the reduction of the edema. In this work, the drug was used under controlled circumstances at various dosage levels in monkeys with traumatically induced edema of the upper extremities. The studies reveal that, when chymotrypsin was given in large doses, the maximum degree of edema reached was less than that in the control animals and that reduction of edema began sooner and was completed more rapidly in the treated animals. These observations suggest that aqueous chymotrypsin can be used effectively in human patients with traumatically induced edema of the extremities.