We report a photoelectron spectroscopic investigation of a series of divanadium-oxide clusters V2Ox- (x=3-7). Well-resolved spectra were obtained at three photon energies (355, 266, and 193 nm), revealing the structural and electronic evolution as the number of oxygen atoms increases in the cluster series. A behavior of sequential oxidation was observed in V2Ox- for x up to 5: low binding energy features with primarily V 3d characters were disappearing in numbers and simultaneously shifting to higher binding energies with increasing oxygen content as a result of V-->O charge transfers. Finally, for V2O6- and V2O7-, the photoelectron spectra exhibit very-high-binding-energy features characteristic of O 2p characters. Vibrationally resolved spectra were obtained for the ground-state features of V2O4-and V2O6-, with a spacing of 1090 cm(-1) (V2O4) and 800 cm(-1) (V2O6), which are assigned to V-O stretching vibrations. Electron affinities are reported for V2O3 to V2O7, and those of 5.61 eV for V2O6 and 5.38 eV for V2O7 are among the highest electronic affinities ever reported. The data are compared with previous theoretical calculations.