The results of investigations on the thermal behaviour of wood, wood treated with creosote, and of creosote are reported. Thermal analysis coupled with ion impact mass spectrometry as well as thermolysis in the modified Bayer-ICI-Shell combustion apparatus (BIS) were applied. The emission products from the BIS-apparatus were analysed qualitatively and quantitatively by gas chromatography coupled with a mass selective detector (GC/MSD). It is shown, that the degradation of creosote and wood treated with creosote is starting with a drying process of the wood around 75 degreesC, followed by evaporation of the creosote compounds between 180 and 400 degreesC. Wood itself is decomposed in an anaerobic process between 300 and 340 degreesC, followed by an oxidative process around 400 degreesC. The oxidative decomposition and mineralisation of creosote takes place between 400 and 600 degreesC with a maximum at 540 degreesC.