Abstract Toxicity of vanadium on cells is one of the less studied effects. This prompted us to study the structural effects induced on neuroblastoma and erythrocytes by vanadium (V) sodium metavanadate. This salt was incubated with mice cholinergic neuroblastoma cells and intact human erythrocytes. To learn whether metavanadate interacts with membrane lipid bilayers it was incubated with bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE). These are phospholipid classes located in the outer and inner monolayers of the human erythrocyte membrane, respectively. Exposure of neuroblastoma cells to metavanadate showed significant decreases in cell viability as well as in cell number correlating with inhibition of aconitase activity. In scanning electron microscopy (SEM) and defocusing microscopy (DM) it was observed that induced on erythrocytes the formation of echinocytes. However, no effects were obtained when metavanadate was made to interact with DMPC and DMPE multibilayers and liposomes, assays performed by X-ray diffraction and differential scanning calorimetry (DSC), respectively. These results imply that the effects of metavanadate on erythrocytes are through interactions with proteins located in the membrane outer moiety, and could still involve other minor lipid components as well. Also, partly unsaturated lipids could interact differently the fully saturated chains in the model systems.