Abstract Cyanoacetohydrazide 1a reacts with 2-arylhydrazoketons 2a, b and 3a, b in refluxing ethanol to yield pyrido [5′, 4′: 2, 3][1, 3, 4] oxadiazolo [3, 2-a] pyridine and pyridazine derivatives; in the absence of solvent pyrazolo [1, 5-a] pyrimidine derivatives were obtained. The reaction of 2a, b and 3a, b will) benzoylhydrazine afforded 1, 3, 4- oxadiazole and pyrazole derivatives.