Carotid end-to-end microvascular anastomoses (MVA) were performed in 100 rats [50 spontaneously hypertensive (SHR); 30 spontaneously hypertensive stroke-prone (SHR-SP); and 20 normotensive controls (WKY)]. Animals were sacrificed at various intervals from immediately after anastomosis to 60 days after surgery, and vascular healing was studied with the scanning electron microscope. In this manner vascular healing in normotensive rats (WKY) could be compared with that in hypertensive rats (SHR and SHR-SP) with vascular disease. Results of this study suggest that vascular healing in hypertensive rats is delayed when compared with normotensive controls. Furthermore, suture material was occasionally incompletely endothelialized in hypertensive animals as long as 60 days after surgery and served as a potential source of emboli. Additionally, an increased susceptibility of hypertensive endothelium (SHR and SHR-SP) to clamp and needle injury was apparent. In spite of this, there was a 100% patency rate of all anastomoses performed, indicating that patency, per se, is unaffected by hypertensive vasculopathy.