Abstract The reaction of anthranilic acid hydrazide with carbon disulfide in alkaline medium yields 5-(2-aminophenyl)-2, 3-dihydro-1, 3, 4-oxadiazole-2-thione rather than 3-amino-2- thioxo-1, 2, 3, 4-tetrahydroquinazolin-4-one. The structure of the product was proved by spectral methods and chemical transformations.