A new vanadium (IV) complex with the monoanion of 2,3-dihydroxypyridine (H 2 dhp), or 3-hydroxy-2-(1H)-pyridone, was synthesized, characterized by physicochemical techniques and tested biologically. The EPR data for the [VO(Hdhp) 2 ] complex in DMF are: g x = 1.9768, g y = 1.9768 and g z = 1.9390; A values (10 -4 cm -1 ): A x , 59.4; A y// , 59.4; A z , 171.0. The mV=O band in the IR spectrum of the complex is at 986 cm -1 . The complex is paramagnetic, with l eff = 1.65 BM (d 1 , spin-only) at 25°C. The irreversible oxidation process [V(V)/V(IV)] of the [VO(Hdhp) 2 ] complex, as revealed in a cyclic voltammogram, occurs at 876 mV. The calculated molecular structure of [VO(Hdhp) 2 ] shows the vanadium(IV) center in a distorted square pyramidal environment, with the oxo ligand in the apical position and the oxygen donor atoms of the Hdhp ligands in the basal positions. The ability of [VO(Hdhp) 2 ] to mimic insulin, and its toxicity to hepato-biliary functions, were investigated in streptozotocin-induced diabetic rats and it was concluded that the length of treatment and the amount of [VO(Hdhp) 2 ] administered were effective in reducing experimental diabetes.