In regulated industries, estimating the weighted average cost of capital (CMPC) is important to the regulatory framework in order to establish both the fair return to the capital providers (investors and creditors) of the regulated companies, as well the reasonable price of goods or services for the customers. The regulated industries provide, in general, basic or infrastructure services and, as the whole society is affected by decisions about this cost, the determination of such is an important part of the regulators activities. The theoretical foundations supporting the concept of the weighted average cost of capital (CMPC) date back to the 1950 s and are solidly established in the academic and business circles, as well as in the regulating entities. The methodologies applied to estimate the expected weighted average cost of capital (CMPC) in future years generate, however, some controversy among the authors. In addition, difficulties exist in gathering the necessary data, especially in emerging markets with small capital markets and a short history of political stability. The objective of this dissertation is to analyze the methodology employed by Agência Nacional de Energia Elétrica - ANEEL (Brazilian National Agency for Electricity - the country s regulator of electricity generation, transmission and distribution) in the calculation of the weighted average cost of capital (CMPC) used in the tariff review process for the electricity distribution companies.