A major restructuring of the Colombian electric power sector is being implemented based on the improvement of sector efficiency through the promotion of a competitive energy market and the participation of private investment. This short presentation highlights major events and difficulties in the restructuring process. The national interconnected power system has an installed generation capacity of about 10,000 MW, of which 80% is hydro and 20% is fuel-fired thermal. The current generation expansion plan calls for the installation of about 4,000 MW during the next 10 years, of which 60% is in thermal plants.