A new oxovanadium(IV) chelate [VOL] (L: N-1-2,4-dihydroxybenzylidene-N-4-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato) was synthesized and characterized by elemental analysis, conductivity and magnetic measurements, LTV-vis, IR, EPR spectroscopy and mass spectrometry. The biochemical and immunohistochemical effects of the administration of the vanadium complex (VOL) into the pancreas of normal and streptozotocin-induced diabetic rats were profoundly investigated. The animals were randomly divided into four groups. Group I: control (intact) animals. Group H: control animals administered with VOL. Group III: STZ-induced diabetic animals. Group IV. STZ-induced diabetic animals administered with VOL. VOL was given to some of the experimental animals by gavage at a dose of 0.2 mM/kg every day for 12 days. Blood samples were collected from animals, on 0 and 1, 6 and 12 days after STZ injection. On day 12, the pancreatic tissues were taken from the animals. The tissue sections were labelled with streptavidin biotin peroxidase technique for insulin. In the diabetic group, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were increased. But, in the diabetic + VOL groups, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were reduced. In the diabetic group, a decrease in the pancreatic glutathione levels, glutathione peroxidase and superoxide dismutase activities and an increase in the pancreatic lipid peroxidation level and catalase activities were observed. The administration of VOL to the diabetic rats reversed this diabetic effect due to its insulinomimetic effects. According to the immunohistochemical and biochemical results obtained, it was concluded that VOL can regenerate B cells of the pancreas in experimental diabetes and has an antidiabetic and protective effects on the pancreas. (c) 2008 Elsevier Masson SAS. All rights reserved.