The dissertation presents three economic essays examining situations where the real options approach can be useful in the definition of regulatory policies, investment strategies and pricing of sovereign risk. The first essay considers the new regulation oriented to interconnection costs of telecommunications networks and proposes adjustments in calculating the return on capital invested in local fixed telephone service. The proposed model establishes the mark- up on the weighted average cost of capital (WACC) to be applied to new concession contracts, taking into account the access option provided by the fixed operator to entrants. The essay innovates by incorporating to the options model the impact of changes in technological paradigms that cause the concessionaire´s demand to fall. The results indicate the robustness of the mark-up in relation to alterations in the model´s basic parameters (fixed-fixed and fixed-mobile traffic and negative demand shocks), and mark-up was estimated to be under 1%. The second essay analyzes investment strategies in real estate development, a sector that involves low liquidity, slow payback and various economic uncertainties related to market demand, price per square meter and land cost. The essay analyzes strategies for simultaneous and sequential launch of real estate projects. The first involves lower construction cost, but comes associated with more uncertain results. Sequential launch presents characteristics similar to real options because it has a series of built-in opportunities regarding the acquisition of information and delay or abandonment of the project. We present a case study of a development in the city of Rio de Janeiro, identifying the optimal strategy and the maximum land cost. Sequential launch aggregates 10% extra value to the undertaking, besides reducing the developer´s risk exposure by over half in comparison with the traditional discounted cash flow method. Finally, the third essay examines sovereign risk and proposes a model from the theory of options and contingent assets to analyze the term structure of four emerging countries (Brazil, Mexico, Russia and Turkey) that together represented on average 54% of JPMorgan´s EMBIG index in the 2000-2005 period. The real exchange rate, modeled as a simple diffusion process, is considered as indicative of default. The calibrated model indicates that in the period studied, the market systematically underpriced Brazilian bonds by an average of 100 basis points, while for Mexico, Russia and Turkey it fairly priced the sovereign debt. The essay also provides the implicit probability of the issuer´s default, a fundamental variable for pricing credit derivatives, a market that has grown at a dizzying pace since the Asian and Russian crises, rising from US$ 180 billion in 1996 to an expected value of US$ 20 trillion at the end of 2006. This market is recognized as being responsible for containing the contagious effects and maintaining the stability of the financial market in recent crises, such as the corporate meltdowns of WorldCom, Parmalat and Enron, among others.