AbstractVasospasm is known to be present during most microvascular procedures. Not until recently has microsurgery made it possible to directly observe the dynamic nature of vascular spasm. This report reviews the physiologic events and the causes of vascular spasm during microsurgery. The current research models and the use of spasmolytic agents to relieve spasm are outlined. Future research in specific areas that pertain to the cremaster muscle model and the future direction and need for research in this area are discussed.