Convergent-beam electron diffraction has been used to determine the space groups of beta- and gamma -Zn-3(VO4)(2) particles in vanadium oxide-doped zinc oxide varistors. The crystal structure of beta -Zn-3(VO4)(2) has been determined to be monoclinic with space group P2(1) and lattice parameters of a = 9.80 Angstrom, b = 8.34 Angstrom, c = 10.27 Angstrom, and beta = 115,8 degrees, whereas that of gamma -Zn-3(VO4)(2) is monoclinic with space group Cm and a = 10.40 Angstrom, b = 8.59 Angstrom, c = 9.44 Angstrom, and beta = 98.8 degrees. Energy-dispersive X-ray microanalysis of these two phases shows significant deviations from their expected stoichiometry. It is apparent that the beta -phase is, in fact, the metastabre Zn4V2O9 phase, whereas the gamma -phase either is a new oxide that consists of zinc, vanadium, and manganese or, more likely, is a zinc vanadate phase with a Zn:V atomic ratio of 1:1 that has the ability to go into solid solution with manganese.