OBJECTIVE: To evaluate quantitative changes in arterial blood flow in the legs and systemic changes in blood flow after hot pack therapy on a leg. METHOD: It was conducted on 60 legs of 30 adults without the symptom of peripheral vascular disease. The blood flow of both popliteal arteries were recorded before and after hot pack therapy on a leg. Also, the blood pressure and pulse rate were recorded every two minutes using a pulsimeter. T-test was done to examine differences between blood flow of the popliteal artery on both legs before and after hot pack therapy. Paired t-test was used to examine differences in each leg before and after hot pack therapy and systemic effect after hot pack therapy. RESULTS: After hot pack therapy, there were statistically meaningful changes in all the variables except the popliteal arterial diameter in a leg with hot pack therapy, whereas there were no significantly meaningful changes in a leg without therapy. Pulse rate was changed significantly, but blood pressures were not. CONCLUSION: There were an increase in regional arterial blood velocity and blood flow, skin temperature, and a reduction in peripheral resistance in a leg with hot pack therapy, but no meaningful changes without thrapy. There is no evidence of reflex vasodilatation. There is no meaningful changes in blood pressure, but an increase in pulse rate.