The endotely of the vascular wall represents a natural antithrombogenic layer in intimal contact with the bloody flow. The waited success of the artificial prosthesis as replacers of minor vessels was not reached. Basically, its poor results were caused by the lake of endothelialization on the prothesical material. A cellular lap on the prosthesis, previously to the implant, could be a good resolution to this problem. If we studied the possibility to obtain a stable, endothelial monolayer "in vitro" before to the "in vivo" implant of the vascular prosthesis. We studied the role of fibronectin as a mediator between the substract and the endothelial cell. Changes on fibronectin when it is added on the culture medium were also analyzed. Although fibronectin has some positive effects as a biologic "glue" previously to the implant to the prosthesis, our results show that after the implant, fibronectin could cause a toxic effect on the adherence and survival of the endothelial cells.