Reaction of one equivalent of vanadium(III) chloride with three equivalents of l-cysteine(H 2Cys) in methyl alcohol affords a V III-Cys compound that is formulated as [V III(Hcys) 3] · 2HCl · 2.5H 2O 1. The solid state characterization of 1 was performed by microanalysis, circular dichroism (CD) and infrared studies as well as room temperature magnetic susceptibility. These studies have shown coordination of each HCys − ligand to the V III atom through an amine nitrogen and a carboxylate oxygen atoms. Solution studies of 1 were carried out in water and methanol by UV–visible, CD and electron paramagnetic resonance (EPR) spectroscopies. According to these studies, it was evident that despite the progressive oxidation of 1 to oxovanadium(IV) species, some V(III) species were also present in solution after several hours. Compound 1, V IVOSO 4 · 5H 2O and l-cysteine were examined for their total antioxidant capacity (TAC) and lag time. Compound 1 exhibited significantly greater total antioxidant capacity and lag time values than l-cysteine. V IVOSO 4 · 5H 2O did not show any total antioxidant capacity or lag time. The inhibition of neutral endopeptidase (NEP) activity caused by 1, V IVOSO 4 · 5H 2O and thiorphan was also measured. Compound 1, at a concentration of 10 −3 M, showed inhibition of NEP activity as potent as thiorphan at 10 −6 M, while V IVOSO 4 · 5H 2O in the same concentration exhibited less than 50% inhibitory activity than that of thiorphan at 10 −6 M. Moreover, the antimetastatic effects of compound 1, l-cysteine and V IVOSO 4 · 5H 2O were examined on Wistar rats, treated with 3,4-benzopyrene. The results revealed that 1 prevents significantly lung metastases (only 9.5% of animals treated with 1 showed metastases), whereas 47–52% of the rats of the control group and those treated with l-cysteine and V IVOSO 4 · 5H 2O exhibited metastases.