A series of novel, functionalized catecholamines (congeners) has been synthesized in which, formalistically, the N-isopropyl group of isoproterenol has been extended by a linear alkyl chain of varying length, terminated by a carboxyl group. Model amide derivatives have also been prepared in order to optimize the biological activity of these derivatives and also to aid in the design of appropriate peptides for the synthesis of conjugates. As a result of these studies, a series of amino acid and monodisperse peptide carriers, containing p-aminophenylalanine as the point of attachment for the drug, was prepared, together with the corresponding conjugates. In uitro and in uiuo evaluation of the congeners, model amides, and conjugates has demonstrated that the biological activity of these derivatives is extremely sensitive to structural modifications a t a point far-removed from the pharmacophore, in both the congener amide and conjugate series. A number of the model amides and conjugates have proven to he highly active when tested in both in uitro and in uiuo test systems. The implications of these results in terms of a novel structure-activity approach to drug design are discussed.