Male Wistar rats weighing 280g were subjected to the stress condition in which the rats were thrusted unceasingly and harassingly with a bamboo stick by the reseacher, for twenty minutes a day for a period of three and twelve months. The blood pressure reached a high mean value (191±3 S. E.) in twelve months. Mean organweight to body-weight ratios of heart, kidney and adrenal gland when compared to nonstressed controls were increased, and that of thymus was decreased. One of the animals subjected to the stress developed significant vascular pathology in the form of panarteritis like arteriopathy and simple fibrous intimal thickening, and others disclosed nothing of vascular changes. The analysis of relative thickness of media to radius in the branches of coronary arteries resulted in no change between subjected rats and controls in thickness of media, compared to that of spontaneously hypertensive reats (SHR) which disclosed medial hypertrophy.