Forty experimental anastomoses have been prepared with the help of polyethylene tubes on the hearts of 10 human corpes, 2 pigs and 16 dogs. In dogs the left internal mammary artery was anastomized with one of the coronary branches of the moving heart without extracorporal circulation. The plastic tube was moved in the vessel by means of a thread attached to the end of the tube and the tube was retrieved by the same thread before the closure of one of the suture lines. The method is illustrated on schemiatic diagrams and its advantages are pointed out.