Diffuse Correlation Spectroscopy (DCS) is a noninvasive optical technique to measure the speed of blood flow using the diffusive nature of light propagation in a living tissue. An advantage of DCS over existing techniques of blood flow measurement is that it can give an index of blood flow velocity (Blood Flow Index: BFI) of blood vessels at an arbitrary depth from the skin surface. In order to utilize this advantage of DCS to diagnose peripheral artery diseases, appropriate protocols to test the vasoreflex responses should be determined. We therefore conducted postocclusive reactive hyperemia test (RHT) in four adult males (22-23 yo) without previous history of peripheral vascular diseases, changing two parameters of (1) the occlusive cuff pressure (0 or 20mmHg higher than the systolic blood pressure) and (2) the duration of arterial compression (1, 3, or 5 min). Previous studies suggested that a phenomenon called overshoot, a transient increase of BFI and its returning to the baseline after cuff deflation, is an index of microcirculatory reactivity. We therefore investigated the parameters of the RHT that give clear overshoot responses in healthy subjects. Source and detector probes were attached with 5 mm interval on the right forearm and a cuff were wrapped around the right upper arm to give occlusion. We found clear overshoot response in case of cuff pressure of 20mmHg higher than the systolic blood pressure, whereas we did not in case of cuff pressure that is equal to the systolic blood pressure. The longer the duration of compression, the longer the time-to-peak of the overshoot response of BFI. Peak amplitudes of the overshoot response were comparable between 1 and 3 min of compression, whereas those between 3 and 5 min were significantly different (p=0.02); the longer duration resulted in the larger overshoot response. However, the signal to noise ratio was poor in 1 and 5 min of compression and the latter caused bruises at the compression site. From these results, we concluded the appropriate protocol for RHT in DCS would use 3 min of cuff compression at 20mmHg higher than systolic blood pressure.