Using the Fisher 344 rat model and blood vessel ring segments in vitro, age-related changes in vascular beta adrenergic relaxation were investigated. In the pulmonary artery and aorta, maximum isoproterenol-induced relaxation and sensitivity to isoproterenol declined from 1 to 3 months of age confirming previous reports. In animals 6 months of age, these vessels no longer relaxed to isoproterenol. In the jugular vein, in which beta adrenergic mechanisms predominate, there was no change in maximum relaxation to isoproterenol or in EC50 values in animals 3 to 27 months of age. Furthermore, determination of propranolol dissociation constants (KB) showed no change in affinity up to 27 months of age. Thus, in venous smooth muscle, in contrast to arteries, beta adrenergic relaxation is well maintained through senescence.