November 15, 1998 marks the 40th anniversary of the commissioning of the first generator at Wairakei geothermal power station, in New Zealand. At that time it was only the second geothermal plant in the world to begin commercial operation and the first to exploit a wet geothermal resource. This paper briefly traces the development and operational history of this pioneering development and in particular the efforts made to keep the plant supplied with steam