This letter considers the multiyear transmission expansion planning model HIPER (acronym of its name in Spanish: "Herramienta Interactiva para la Planeacion de la Expansion de la Red"), developed for application in deregulated environments. HIPER allows transmission planning under great uncertainties, such as the generation expansion, by defining strategic scenarios to reflect the possible future evolution of the generation system and the incorporation of a decision analysis scheme to minimize the risk of the proposed plan. An example case illustrates how HIPER can be applied to propose a transmission expansion plan, which is robust enough in the face of the uncertainty in the generation expansion.