We have evaluated the durability of the renal parenchyma and the optimal force for the suture tightening without risk of the tissue eruption on the cadaveric material from both sexes. We have used „Dexon II” as a suturing material and original eruption device for investigations. Re-sistance of the materials to plastic deformations was used as ground for mathematical calcula-tions. Direct correlation was detected between the thread diameter and parenchyma eruption. Tension analysis supposed that by increase in diameter it is possible to apply more tightening strength without risk of eruption. Manual and tactile exercises at the training simulator are im-portant for development of surgical skills with regard to tightening of surgical suture.