Regional heat loss and skin temperature changes in 25 healthy, full-term infants were studied under controlled conditions at environmental temperatures of 28-32 degrees C. Skin temperatures for all body regions followed changes in operative temperatures. Regional dry heat losses closely followed the external temperature gradient (difference between skin and operative temperature). The technique allows measurement of regional dry heat loss from the newborn skin exposed to different environmental conditions for different body surface areas. Thermal conductance, as an index of cutaneous blood flow, was calculated in a subgroup of 8 of the 25 babies by decreasing the operative temperature by 3-4 degrees C from the assumed thermoneutal zone. Thermal conductance indicated that only the foot responded to lower temperatures with vasoconstriction. Blood flow index of the chest region increased in all babies at lower temperatures.