In spontaneously hypertensive (SHR) and normotensive (WKY) rats fed different diets, blood pressure (BP) increased significantly in both strains when the carbohydrate (CHO) source was from refined rather than from natural ingredients. This BP increase was observed whether sucrose, glucose, or starch was the principal CHO. Urinary excretion of norepinephrine, dopamine, and, to some extent, epinephrine also increased, while myocardial concentrations were unaffected. Despite a comparable elevation of catecholamine excretion in both SHR and WKY rats fed high amounts of refined CHO, the BP increases were greater in the former. The strain differences were explained by the known dissimilar response of their blood vessels to catecholamines. The results suggest that BP elevation after high CHO ingestion is mediated via increased catecholamine production and/or release, thus implying a neurogenic mechanism.