Vascular smooth muscle from femoral arteries of hypertensive rats contract autorhythmically in vitro, whereas medial smooth muscle cells from normotensive animals are normally quiescent. This behavior suggests improved intercellular communication that permits pacemakers to control large numbers of cells. We used a transmission electron microscope to search for structural evidence of such change. In the medial arterial tissue of hypertensive rats, we found pedishaped projections extending from one cell and forming a close apposition with the smooth muscle surface of a neighboring cell. Comparable structures were not found in the normotensive controls. However, numerous other forms of close appositions were found in the tissues from the hypertensive and normotensive rats. The presence of the unique pedishaped projections in the hypertensive tissue suggest a physical means of intercellular communication permitting enhanced pacemaker influence. Perhaps these projections are formed in response to the hormonal environment seen prior to and during renal hypertension.