Four kinds of vanadylcomplexes of hydroxyazine-type heterocycles were synthesized. Bis(1,2-dihydro-4,6-dimethyl-2-oxo-1-pyrimidinolato)- and bis(1,2-dihydro-2-oxo-3,5,6-trimethyl-1-pyrazinolato)oxovanadium(IV) complexes showed higher insulin-mimetic activity than vanadyl sulfate as a positive control.