This paper compares the spontaneous combustion of two Victorian brown coals and a Pakistan lignite with that of products of the same coals which have been dried, mainly by the mechanical thermal expression technique (MTE) in which aqueous slurries of the materials are heated (125 or 200 degrees C) and pressed (5-15 MPa). Samples of briquettes obtained by steam heating and pressing from a similar Victorian coal have also been studied. The amount of residual moisture in the dried samples had the largest effect on T(crit) values. The inorganic content of the samples varied and may also have contributed to the changes. T(crit) increased with increasing particle size for the dried coals and MTE samples. There was no obvious correlation between T(crit) and pore volume. (C) 2009 Elsevier Ltd. All rights reserved.