The role of changes in cutaneous (below the skin) blood flow in MDMA-induced hyperthermia was examined by measuring blood flow in rabbit ears via implanted ultrasonic probes after i.v. injection of 3 or 6 mg/kg MDMA, and also by measuring core temperature after MDMA. Cervical sympathectomies were performed on some rabbits to see whether changed blood flow to the ear was at least partly controlled by the sympathetic system, and the effects of ambient temperature were investigated by placing rabbits in cool, "room temperature" and warm environments. MDMA dose-dependently increased core body temperature while reducing blood flow in the rabbit ear pinna. Cervical sympathectomy prevented reduction in blood flow in the denervated ear, but not in the non-denervated ear, after MDMA. Sympathectomy also reduced MDMA-induced increases in core temperature, but only at 6 mg/kg. In contrast to findings with rats, MDMA always increased core temperature in all environments (cool, room temperature and warm). These findings suggest that MDMA may promote hyperthermia, in part, by reducing cutaneous blood flow (cutaneous vasoconstriction), hence reducing heat-loss mechanisms operating through the skin, and that this effect may be modulated through the sympathetic system.