1,4-benzodiazepine-2,5-diones were synthesized by a simple procedure utilizing polymer supported amino acids and o-nitrobenzoic acids or protected anthranilic acids. Cyclization of the common aminoamide intermediate with concomitant release from the support furnished the desired 1,4-benzodiazepine-2,5-diones. The products were recovered in high yields and exhibited excellent purities.