The diatomic molecule vanadium oxide, VO, and its charged species VO+ and VO- were studied by multireference and coupled cluster methods in conjunction with large basis sets. The investigation of 22 states and the construction of 21 full potential energy curves allowed for a detailed understanding of the electronic structure of these species. Our best binding energies for the ground states of VO (X-4 Sigma(-)), VO+ (X-3 Sigma(-)), and VO- (X-3 Sigma(-)) were D-e = 150, 138, and 143 kcal/mol, respectively, in harmony with the corresponding experimental values. For both species VO and VO+ and for all states studied, the bonding showed a strong ionic character conforming to the models V+O-and V2+O-.