The effects of solvent/coal (S/C) ratio and demineralization on the solubilization of Turkish coals (Tuncbilek, Mugla-Yatagan, Beypazari lignites and Zonguldak bituminous coal) in tetralin by microwave energy have been investigated. Particle size distributions and the surface area of the coals decreased with demineralization. For the investigation of the effect of the S/C ratios with values of 8/1, 10/1 and 12/1, the coal samples were heated by microwave energy for 20 min. The result indicated that the optimum S/C ratio was 8/1. The effect of microwave heating period was investigated at this value and the heating period was changed from 5 to 20 min at 5-min intervals. It was found that THF solubles yields of original coals were higher than those for demineralized coal except for Mugla-Yatagan lignite. (c) 2005 Elsevier Ltd. All rights reserved.