Complications of the pneumatic tourniquet used during limb surgery result from excessive direct pressure. Traditional recommendations suggests parameters for maximum pressure and time limits rather than the minimal effective pressure to achieve a bloodless field. A clinical study was undertaken to evaluate the pneumatic tourniquet setting required for adequate haemostasis in the upper limb. The correlations between several possible influencing parameters (age, sex, arm fat thickness, extremity length, systolic, diastolic, and mean blood pressures) and the minimal pneumatic tourniquet pressure at which the peripheral pulse reappeared were studied in 50 patients undergoing surgery, using a Doppler stethoscope. The average Doppler Opening Pressure was 168.5 ± 42.7 mmHg and the only significant clinical variable was the mean blood pressure. From these results an equation was derived to predict the minimal effective tourniquet pressure. The mean calculated tourniquet pressure was 202.3 ± 34.2 mmHg, well below the 250 to 300 mmHg previously recommended. The technique consisted of inflating the tourniquet to a pressure of 300 mmHg, then reducing it to the calculated value. A bloodless field was maintained in all patients.