In a series of experiments on the aorta of the rat, the behaviour of an absorbable monofilament suture VICRYL (Polyglactin 910) was compared to that of a non-absorbable suture ETHILON (Polyamide 6/6). A total of 86 rats was operated upon and examined over a period of 70 days. The report includes a complete description of experimental procedures and techniques used during the operations. The evaluation of the experiments took place after completion of the mechanical, histological and scanning electron microscopical tests. It has been proven that under similar conditions, the 0,2 metric suture VICRYL has adequate tensile strength to withstand the intravascular pressure in a vessel with an outer diameter of approx. 1,5 mm. Aneurysm, stenosis and dehiscence of the anastomosis did not occur. The VICRYL suture showed no reactive processes after a period of 42 days. With the suture ETHILON the inflammation of the media and the hyperplasia of the intima persisted even after 70 days, at the end of the experiment. It is therefore shown in microsurgery, the monofilament absorbable suture VICRYL and the non-absorbable monofilament suture ETHILON are equal in their mechanical qualities, but that the suture VICRYL has by far the better tissue compatibility.