Skin-surface temperature gradients (forearm temperature - fingertip temperature) have been used as an index of thermoregulatory peripheral vasoconstriction. However, they have not been specifically compared with total finger blood flow, nor is it known how long it takes fingertip temperature to fully reflect an abrupt change in finger blood flow. Steady-state skin-temperature gradients were compared with total fingertip blood flow in 19 healthy volunteers. There was an excellent correlation between steady-state skin-surface temperature gradients and total fingertip blood flow measured with venous-occlusion volume plethysmography: gradient = 0.2-5.7.log(flow), r = 0.98. The half-time for fingertip cooling after complete arterial obstruction (in 8 volunteers) was 6.6 +/- 1.2 min. The authors conclude that skin-temperature gradients are an accurate measure of thermoregulatory peripheral vasoconstriction.