In 1998 a survey was made of the termites of the Leuser Ecosystem (in Sumatra, Indonesia), which includes a substantial area (c. 1 million ha) of unbroken primary rain forest. Nine sites and an altitudinal gradient were sampled. Altitude had a significant effect on species richness, which declines with even a 100-m increase in altitude. Species composition too was significantly affected by altitude. Functionally, only termites in one feeding group (II, which forage outside of their nests) were significantly affected by altitude. A mid-altitude termite species assemblage was evident. Longitude also significantly affected species composition; Macrotermitinae were numerous on the western side of the Ecosystem and Termitinae and Nasutitermitinae more numerous to the east of it. This was probably due to differences in rainfall patterns across the Ecosystem.