After of the incidence of innumerable problems related to voltage instability phenomena, the control of reactive power in electrical power systems became an important issue in the last years. The adequate control of the voltage for a specific area can prevent this kind of problem. With this objective, voltage control areas are established from an eigenvalues and eigenvectors analysis of the sensitivity matrixes: VCS Voltage Control Sensitivity Matrix and QV. The sensitive matrix [VCS] is form by diagonal elements that relate to the controlling variables and to the controlled voltage (controlled variable), and the analysis of the sign of each diagonal element indicate if a specific control action is adequate or not. The off-diagonal elements represent the interdependence among the voltage controller equipments. The sensitivity matrix QV, called [JSQV] is obtained from the Jacobean matrix from the linear load flow equations. The voltage control areas recognized from the eigenvalues and eigenvectors analysis to each sensitivity matrix are coherent. Also, voltage control areas were identified directly from sensitivity matrixes. These areas were compared founded coherent results.