We have developed a new method for the synthesis of 2-formyl-thiazole 3-oxide and 2-formyl-4-methylthiopyridine 1-oxide. Several new p-tosylhydrazones of pyridine, thiazole and imidazole derivatives were prepared. It was found that some of the hydrazones of the pyridine 1-oxides series were active in vivo against ascites sarcoma 180, whereas p-tosylhydrazones of the azole-N-oxide series were less active or inactive.