Phlebothrombosis model was elaborated in experiment. The thrombotic mass was obtained in vitro, mixing the blood of animal with thrombin. Retracted thrombus was injected by puncture into previously ligated segment of the dog's v. jugularis externa. The vein's preparation was studied up on 1, 3, 5, 7, 10th and 14th day. Up to 8-10 days the thrombus adherence to the vein wall is friable and it is possible to extract it with the help of balloon catheter. Endothelium desquamation was revealed starting from 3-5th day.