Under controlled conditions the effects of various "sympatholytic" agents on the cardiovascular responses to epinephrine and norepinephrine were compared in man. The dosages of the sympatholytic drugs administered approximated those usually employed clinically. Such basic data are given for the following agents: Dibenamine, the imidazoline derivatives [Priscoline and Regitine (C-7337)], the dihydrogenated alkaloids of ergot (D.H.K. and C.C.K.), L-hydrazinophthalazine (C-5968), tetraethylammonium, and hexamethonium (C6).