Nine men were subjected to four temperature exposures: (A) sauna and head-out ice water immersion; (B) sauna and 15 degrees C shower; (C) sauna and room temperature; (D) head-out ice water immersion and room temperature. Exposures were repeated and ended with a 30-minute recovery. Heart rates were recorded continuously and blood pressures were determined six times during each experiment. Rate pressure products and indications of cardiac stroke work were calculated from the data. The results demonstrated decreased total peripheral resistance (TPR) to the blood flow in response to the heat of the sauna (C), with concurrent increase in cardiac oxygen demand and negligible increase in the stroke work. Cold exposures (D) increased the TPR. Cold did not increase the cardiac oxygen demand but increased the stroke work. The alternation of heat and cold (A) or cool (B) presented the most intensive strain on the heart.