The equatorial peatlands of the Kutai lowland of eastern Kalimantan are generally 4-10m in thickness but some sections exceed 16m in depth. The deposition of peat commenced about 8000 years ago after shallow flooding of the basin by the Mahakam River. The earliest vegetation is a Pandanus swamp which grades upwards to swamp forest dominated by dipterocarps. The peatland has expanded laterally and rivers have maintained narrow levee-channel tracks through the swamp, which has grown vertically in balance with river accretion. Historical fires are associated with extreme El Niño years of drought, but human agency is important. The fires of 1982-3 and 1997-8 burnt up to 85% of the vegetation on the peatland. Macro-and micro-charcoal analyses show that fire has occurred throughout the history of the peatland. However charcoal is rare in forests remote from rivers until after 3000 years ago and becomes more common within the last millennium. Fires are earlier and more frequent in sites accessible from waterways, and floodplains have been widely burnt down to water table or below, forming extensive lakes. Major peatland fires may have occurred only within the last few centuries.