We analyze and evaluate the evolution of the deregulated market for electricity in Colombia in the period from 1995, when deregulation took place, to 2002. The case of Colombia is of particular interest as it is one of the most open markets in the developing world as well as being predominantly based on hydroelectrical technology. Furthermore, Colombia has had no blackouts since deregulation, in contrast to a number of neighboring countries, even though Colombia has had periods with severe adverse weather conditions. Colombia has so far managed to adjust the regulatory environment to keep investment at a reasonable level. Finally, we discuss the prospects for the Colombian system over the next 5 years. (C) 2003 Elsevier Ltd. All rights reserved.