The use of a pneumatic tourniquet is potentially associated with injury to underlying muscles, vessels, and nerves if excessive pressure occurs beneath the toumiquet. In order to minimize the risk of soft tissue injury, the lowest tourniquet pressure that maintains a bloodless operative field should be used. A clinical study was undertaken to evaluate the pneumatic tourniquet setting required for adequate hemostasis in upper extremity surgery. From March to September in 1984, the subcutaneous soft tissue pressure of the 20 upper extremities beneath a pneumatic toumiquet in the arm were measured directly and the following results were obtained. 1. The underlying subcutaneous soft tissue pressure was not affected by adult, age, arm circumference, and blood pressure of normal range. 2. The underlying subcutaneous soft tissue pressure showed direct correlation with the tourniquet pressure respectively. 3. A tourniquet preasure of more than 250 mmHg was not rarely required in a normotensive individual.