[N,N'-1,3-Propyl-bis(salicyladimine)]oxovanadium(IV) - an oxovanadium complex has been tested for bioactivity as an insulin-enhancing agent. Its structure reveals that the vanadium(IV) ion is hexacoordinated and situated in a distorted octahedral environment. The complex was administered intragastrically to both normal and streptozotocin (STZ)-diabetic rats for two weeks. The results showed that the complex, at a dose of 10.0 and 20.0mgV.kg(-1), could lower the blood glucose level in STZ-diabetic rats and improve the response to an oral glucose challenge. This complex did not alter these parameters in normal rats. It was suggested that the complex exerted an antidiabetic effect in STZ-diabetic rats.