In Indonesia, energy consumption (excluding non-commercial energy) increased from 328 MBOE in 1990 to 478 MBOE in 1995. As a consequence, energy sector CO2 emissions increased from 150 million tons to over 200 million tons during the same period. The present rapid economic growth Indonesia is experiencing (7-8%) will continue in the future. Based on a BAU scenario, primary energy supply for the year 2020 will be 18,551 PJ, an increase of 5.9% annually from 1990 CO2 from the energy system will increase from 150 Teragrams in 1990 to 1264 Teragram in 2020. The mitigation scenario would reduce total CO2 emissions from the BAU scenario by 10% for the year 2000 and 20% by 2020. Some demand side management and energy conservation programs are already included in the BAU scenario. In the mitigation scenario, these programs are expanded, leading to lower final energy demand in the industrial and residential sectors. Indonesia’s total primary energy supply in 2020 is approximately 5% lower for the mitigation scenario than for the BAU scenario. In the BAU scenario, coal and ail have the same contribution (25%). In the mitigation scenario, natural gas and nonfossil fuels such as hydropower,geothermal, and nuclear have higher contributions.