In 1997, the entire Indonesian archipelago suffered from serious droughts associated with the climatological phenomenon known as El Nino Southern Oscillation. This resulted in an unprecedented fire episode where more than 99 million hectares of land were burnt in Indonesia. Smoke from the fires hung as a huge blanket over Souteast Asia, covering large cities such as Kuala Lumpur and Singapore, restricting traffic (air, sea and land) and causing a severe health hazard. The smoke originated mainly from fires in Sumatra and Kalimantan. Anaysis of the number and distribution of fires (detected as 'hot spots' by NOAA satellite imagery) indicates that the distribution of fires in time in Sumatra wa very narrow. Of the 31,500 'hot spots' recorded over a twelve-month period starting September 1997, one-third were recorded during a single week (12-18 October 1997). The spatial distribution also showed a narrow spread. Almost a quarter of all fires recorded from September 1997 until July 1998 were in the lowlands of the province of Sumatra Selatan. Although the term 'forest fire' was frequently used, there is no evidence that primary lowland or mountain forest suffered much from burning. What did burn however was swamp forest vegetation and secondary vegetation regrown after logging. The causes of these fires were multiple and diferent from one province to another. One of the main causes though was land clearing for new plantations.