Tourniquets are often used for surgery on the extremities to provide a bloodless surgical field. However, inflation of tourniquet can cause hypertension, and deflation can cause hypotension. Decrease in arterial pH and PaCO2, and increase in PaCO2 immediately following tourniquet deflation have been documented. In 25 patients for the operation on the lower extremity with spinal anesthesia, we examined the changes of arterial blood pressure, heart rate, arterial blood gases (pH, PO2, PCO2, HCC3 ), and serum electrolytes (Na(+), K(+). Cl(+) ) just before inflation of tourniquet and at 5 minutes after deflation of it. The results were as follows ; 1) Systolic blood pressure decreased by 5.8 mmHg (p<0.05), and diastolic blood pressure decresed by 3.8 mmHg after release of tourniquet. But heart rate did not change, significantly. 2) PaCO2 increased bY 2.4 mmHg after deflation of tourniquet, but it was not significant statistically. Arterial pH, PaCO2, and concentration of bicarbonate all showed insignificant changes. 3) All of serum electrolytes showed too small and insignificant changes.