Synthesis of vanadyl(IV) organophosphonates VORPO(3) . nH(2)O (with R = CH3, C2H5, C6H5) has been investigated by reaction of VOSO4 . 5H(2)O + RPO(3)H(2) under refluxing conditions in aqueous media. The influence of different parameters is discussed, and compounds are characterized by X-ray powder diffraction, TGA, IR, XANES, and EXAFS. For example, three crystallographic forms of VOC6H5PO3 .2H2O obtained differ from each other in the location of the trans water molecule in the layered structure.