Twenty-six patients requiring orthopaedic surgery were anaesthetized and oesophageal and rectal temperature were monitored continuously. Twenty patients requiring a pneumatic tourniquet were allocated prospectively to one of two groups: passive group (Pg) with reflective insulation on all available skin surface (n = 10) and forced group (Fg), with active warming by a forced air system (n = 10). Six patients without a tourniquet were used as a reference group (Rg). The pneumatic tourniquet time was similar in the tourniquet groups. During tourniquet inflation, oesophageal temperature increased with time. The difference was significant compared with the reference group at approximately 20 min. At about 30 min, oesophageal temperature in group Fg was significantly higher than that in group Pg. After tourniquet deflation, temperature decreased transiently. Changes in rectal temperature were similar but delayed significantly. A mechanism to explain the increase in core temperature during pneumatic tourniquet use remains unclear. A redistribution mechanism by cooling of the blood in a cold and vasodilated limb could explain the decrease of temperature after tourniquet deflation.