Abstract Several countries have modified the structure of their Electric Energy Markets (EEM) by the introduction of various levels of competence in the generation, transmission and distribution areas, which allows the generators to sell their production at a short-term market price (or spot price). The fundamental premise of the regulation is that the global efficiency can be improved through a strong competence in a market structure governed by explicit rules. The Game Theory is the study of mathematical models of conflict and cooperation between intelligent rational decision-makers. In this paper, the Game Theory is proposed to analyze the economic behavior of the generators to make their offers to the short-term EEM. The IEEE 9-bus system is used to illustrate the main features of the proposed method.