The vascular proteoglycans probably have an important influence on the biomechanical properties of blood vessels and, therefore, may play a role in the development or maintenance of hypertension. In the aorta of the spontaneously hypertensive rat, the authors previously observed (1) an increased content of chondroitin sulfate, (2) an increased incorporation of [35S]sulfate into proteoglycans, and (3) qualitative alterations in the [35S]polysaccharides compared to the normotensive Wistar Kyoto rat. To determine if these differences were related to hypertension or to strain variations, normotensive and hypertensive Dahl S rats were studied. There was a significant elevation (70%) in the aorta content of chondroitin sulfate, whereas the dermatan sulfate and hyaluronic acid contents were similar in the two groups. The in vitro incorporation of [35S]sulfate was increased 2.6-fold in the hypertensive animals. No differences between the two groups were observed with respect to the gel chromatographic profiles of the [35S]proteoglycans or the charge density of the [35S]glycosaminoglycans, as assessed by ion exchange chromatography. It was concluded that the increase in chondroitin sulfate and [35S]sulfate incorporation into proteoglycans occurred as a result of hypertension, regardless of genetic factors.