The abdominal aorta in 56 white rats has been sutured by means of a microsurgical technique in order to study changes that the smooth muscle cells (SMC) of the vascular wall undergo during the restorative process of its integrity and intima formation. The material for histological investigation is fixed in 10% formalin or in Karnoy fluid and embedded in paraffin. For the electron microscopic investigation the specimens of the aorta are treated in 2% and 5% glutaraldehyde solution and in 1% tetraoxic osmium solution and embedded in epon and araldit mixture. The muscular wall SMC actively participate in the reparative processes when the vascular suture is performed by means of the microsurgical technique. The vascular wall SMC ensure the rat aorta restoration in such a way that already 3 weeks after the operation the cut line can be defined only by the presence of the suture thread and by a slight sheet of the connective tissue. Migration and accumulation of the SMC under the endothelium restored its integrity results in the intima formation. Simultaneously, an intercellular substance is forming, that is directly connected with the SMC development.