This book provides a macroeconomic evaluation of EU enlargement is undertaken with extending GTAP and ORANI-INT static/dynamic models taking into account possible integration effects: trade effect, labor mobility, capital movement, emission trading, and marginal abatement cost. The CGE models developed in this book focuses on the energy sector. Taking into consideration of energy and environmental interactions, carbon taxes are imposed on fossil fuels because we account for carbon emissions arising from the combustion of these fuels. Therefore, CO2 emissions are associated with all emitting activities, including current production, capital formation, and household and government consumption. In this book, case studies have been carried out to analyze energy and climate change policies in EU enlargement process using CGE models of energy, economy, and environment interactions. The models have been developed in a framework which allows modification and expansion and expansion in a very convenient manner. Thus, models provide a template to the academics and researchers to meet the challenges posed by the theoretical limitations of the existing CGE models.