We examined the glycosaminoglycan (GAG) components in human pulmonary arteries compared to those in the aorta. Definite changes in GAG contents and components were found between the pulmonary arteries and the aorta. The GAG content of the aorta was constantly higher than that of the pulmonary artery. As to the components of the arterial GAGs, however, hyaluronic acid comprised significantly higher proportions of total GAGs in the pulmonary arteries than in the aorta, whereas dermatan sulfate showed lower proportions in the pulmonary arteries than in the aorta. These significant differences are possibly due to either the effect of the continuously different blood pressure on the wall of these two types of arterial vessels or to constitutional changes of their fundamental structures associated with atherosclerosis.