Thermal springs have been used for bathing, washing and cooking for thousands of years in many countries. At the beginning of this century, experiments started with piping the hot water to houses for space heating and with using geothermal steam for the production of electricity. Geothermal is a proven energy resource that uses mostly conventional technology. Commercial production on the scale of hundreds of MW has been undertaken for over three decades both for electricity generation and direct utilization. Today, electricity is generated from geothermal energy in 21 countries. The installed capacity is nearly 6300 MW-electric. Four developing countries (El Salvador 18%, Kenya 11%, Nicaragua 18% and Philippines 21%) produce over 10% of their total electricity from geothermal. Electric generation cost is commonly around 4 U.S.cents/kWh. Direct utilization of geothermal water (space heating, horticulture, fish farming, industry and/or bathing) is known in about 40 countries, thereof 14 countries have each an installed capacity of over 100 MW-thermal. The overall installed capacity for direct utilization is about 11,400 MW-thermal. The production cost/kWh for direct utilization is highly variable, but commonly under 2 U.S.cents/kWh(t). A worldwide survey shows that the total investments in geothermal energy between 1973 and 1992 amounted to approximately 22 billion U.S.$. During the two decades, 30 countries invested each over 20 million U.S.$, 12 countries over 200 million U.S.$, and 5 countries over 1 billion U.S.$. During the first decade, 1973-1982, public funding amounted to 4.6 billion U.S.$ and private funding to 3 billion U.S.$. During the second decade, 1983-1992, public funding amounted to 6.6 billion U.S.$ and private funding to 7.7 billion U.S.$. Geothermal development has in the past been much affected by the development of prices of the competing fuels, especially oil and natural gas. Assuming a continuation of the present oil prices, the annual growth rate in geothermal utilization is likely to be some 4% for electricity generation and 10% for direct utilization. This would imply installed capacities of 8900 MW(e) and 30,000 MW(t) in the year 2000. The total investment cost of geothermal in the world during the next decade can be expected to be some 15-20 billion U.S.$. Properly implemented, geothermal energy is a sustainable resource and benign to the environment. The emission of greenhouse gases is minimal compared to fossil fuels. The removal of hydrogen sulphide from high temperature steam and the reinjection of spent geothermal fluids into the ground make the potential negative environmental effects negligible. The relative economic viability of geothermal energy will improve significantly if and when a pollution tax is endorsed on power production using fossil fuels. Geothermal exploration and exploitation requires skills from many scientific and engineering disciplines. International geothermal training centres are operated in Iceland, Italy, Japan, Mexico, and New Zealand. The International Geothermal Association was founded in 1988 and has over 2000 members in all parts of the world.