The study of chemical and biological effects of fluorine substitution on the aromatic ring of catecholamines has now been extended to epinephrine (Epi). 2- and 6-fluoroepinephrines (2-FEpi and 6-FEpi) have been synthesized. Fluorine substitution on the 2- or 6-carbon of the aromatic ring alters the selectivity of epinephrine toward alpha- and beta-adrenergic receptors, similar in manner to the change in selectivity seen with norepinephrine (NE). Thus, 2-FEpi is a relatively selective beta-adrenergic ligand, while 6-FEpi is a relatively selective alpha-adrenergic ligand. Fluorine substitution of Epi also can markedly increase potency at either alpha- or beta-adrenergic receptors.