A subset of patients with idiopathic hypertension shows an increase in blood pressure of 10 percent or more in response to salt-loading and have been termed "salt-sensitive" (SS). Limited studies of adrenergic function in response to salt-loading suggest that the response of SS patients may differ from that of non-salt sensitive (NSS) patients. The present studies were designed to examine the response of the adrenergic and dopaminergic systems to salt-loading in SS and NSS patients with idiopathic hypertension.