This paper reports the pollen analysis of an 8 m core from a mire at 445 m altitude and 2°S latitude on ultramafic soils near the western shore of Lake Matano, South Sulawesi. The area is almost undisturbed by humans and the record is believed to cover about 5075,000 yr B.P., with some breaks in the record. A section from 17,000 to around 5500 yr B.P. and the last 1000 years of the record may be missing or disturbed. The results show that montane forest grew around the site continuously through the late Pleistocene with a maximum increase in higher altitude taxa from 35,000 to after 17,000 yr B.P., the time of glacial maxima elsewhere. Also in this period, increases in grass and Casuarina indicate possible drier conditions. The Holocene sections record lower altitude forest with increased taxonomic diversity, including secondary species. The results show that vegetation in the region has been sensitive to climatic change, the Pleistocene ecology being consistent with a temperature change of about 2.53.5°C with a phase up to 50% drier than present. The site climate was possibly affected by shelf exposure in the Gulf of Bone due to lower sea levels. However the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity. A distinctive record of fine charcoal occurs throughout the deposit. This shows that the forest has never been continuously fire-free for a very long time. The cause of the fires may be natural as no evidence for human occupation was discerned.