Plethsymographic recordings are used to evaluate changes in peripheral vascular tonus. Twenty-six volunteers (15 men, 11 women) with a mean age 31 years were included in this study. Plethsymographic recordings were done both at baseline and +4degreesC temperatures bilaterally. Significant reductions in systemic blood flow were noted with different maneuvers. Reactive hyperemia occurring after ischemia was local, however local reduction in blood flow after cold test was systemic. As the local temperature increased, the blood flow parameters normalized, too. In normal controls these values normalized in 20 minutes. The changes in vasomotor tonus due to cold test demostrated a parallel pattern.