A patient temperature control system (10) uses variable temperature gradient warming/cooling in combination with a warming/cooling device (16), such as a blanket, to increase efficiency in driving a patient's temperature to a desired setpoint, with reduced occurrence of and magnitude of overshoot conditions. In operation, the controller (26) of the system (10) senses the temperature of a patient (12) via a sensor (31), for comparison to a temperature of the circulating water, sensed via sensor (30). If the patient temperature is not sufficiently close to a setpoint temperature, the system (10) is operable to warm/cool the circulating water to a temperature which differs from the patient's temperature by a temperature gradient of 10 ° C., or some other preselected initial temperature gradient. After a subsequent time interval, if the patient temperature has not moved sufficiently close to the setpoint temperature, the controller (26) incrementally raises or lowers the temperature of the circulating water, to intensify the a warming/cooling effect. This procedure repeats at desired intervals, to more efficiently reach the setpoint temperature. Thus, the system (10) is capable of automatically increasing or decreasing the temperature gradient, dependent upon subsequently sensed patient temperatures.