A library of 192 structurally diverse 1,4-benzodiazepine derivatives containing a variety of chemical functionalities including amides, carboxylic acids, amines, phenols, and indoles was constructed from three components, 2-aminobenzophenones, amino acids, and alkylating agents, by employing Geysen's pin apparatus [Geysen, H. M., Rodda, S. J., Mason, T. J., Tribbick, G. & Schoofs, P. G. (1987) J. Immunol. Methods 102, 259-274]. Rigorous analytical verification of the chemical integrity and yield of a representative collection of the diverse derivatives was carried out. In addition, the library of derivatives was evaluated for binding to the cholecystokinin A receptor by employing a competitive radio-ligand binding assay. This provided detailed structure versus activity relationships that were confirmed by independent large-scale synthesis and evaluation of several of the 1,4-benzodiazepine derivatives.