TCpO2 [transcutaneous O2 partial pressure] shown to be a reliable indicator of the state of perfusion of the skin in healthy and ischemic legs. It is also shown that TCpO2 can be used to predict the healing potential if amputation is performed. The most meaningful reading is obtained at 10 cm below knee anteriorly. The critical value is .apprx. 35 mm Ag, since the pO2 value for below-knee amputations performed on most patients with a 10 cm below knee amputation was less than this, further surgical treatment was required, while all patients with values above this underwent successful amputation. Determination of the 10-cm below-knee-control site ratio does not appear to provide any further advantage over the absolute 10-cm below-knee site value. The control site measurement should be taken to eliminate central circulatory failure. The technique can be easily undertaken by hospital technicians or regular nursing or junior medical staff. A site reading requires an average of 35 min. The capital outlay is well within the capability of an average general hospital and the running costs are negligible.