In vivo freezing of microarteries is known to relieve spasm without inducing thrombosis. In the present study the process of vascular freezing was investigated in veins using ethyl chloride in the rat model. Two separate experiments were performed. In experiment 1 the epigastric and femoral veins were frozen, and the immediate change in diameter was recorded. Patency rates were evaluated and specimens harvested at 2, 10, and 30 days. In experiment 2 the epigastric and femoral veins were frozen, divided, anastomosed, and examined for patency at 72 hours. Patency in frozen epigastric and femoral veins was 100%. Pathological findings were loss of intima and part of the media layers, and cellular depopulation of the media layer, with progressive regeneration. Increase in vein diameter was statistically significant. In experiment 2, patency rates were 5% at 72 hours for epigastric veins and 100% for the femoral vein. Microthrombi adherent to the wall were demonstrated in all specimens. In conclusion, the freezing of microveins relieves spasm without inducing thrombosis; the frozen veins can be reliably divided and anastomosed in the femoral vein but not in the epigastric vein, the difference being most likely due to the different diameter and flow.