AbstractMerbau wood has been widely used in outdoor applications. However, it has a disadvantage in that its water-soluble extractives readily leach out and stain adjacent materials. Heat treatment is an efficient technique to solve this problem. In this study, the effects of heat treatment on the durability of merbau heartwood were investigated. Merbau heartwood blocks with and without heat treatment were exposed to subterranean termites (Coptotermes formosanus) according to ASTM D3345 (2008), and to brown-rot fungus (Gloeophyllum trabeum) and white-rot fungus (Trametes versicolor) according to ASTM D1413 (2007). The effect of heat treatment on the chemical changes in merbau heartwood and its extracts were investigated by means of Fourier transform infrared spectroscopy (FTIR) and gas chromatography - mass spectrometer (GC/MS). The results show that the extraction yields of merbau heartwood with heat treatment using various solvents significantly decreased. However, termite resistance and fungal resistance of merbau heartwood with and without heat treatment showed no obvious difference. FTIR spectra in the fingerprint region of merbau heartwood and its ethanol-benzene extracts did not show any significant difference between heat-treated and untreated samples. More constituents were identified from the ethanol-benzene extracts of merbau heartwood with heat treatment by means of GC/MS compared to those identified from the ethanol-benzene extracts of untreated merbau heartwood.