The mitogenic activity of thrombin in endothelial cells is not well understood. The inositide metabolism is an ubiquitous transducing mechanism that seems to be involved in the control of cell growth. Thrombin is a potent stimulant of the release of inositol phosphates in platelets. The data presented here suggest that thrombin is able to induce competence in pig aorta endothelial cells to proliferate in response to insulin. Also thrombin is a potent stimulant of the inositide metabolism what suggests that the activation of this pathway might be at least one of the mechanisms through which thrombin induces competence in this cells.