Four coals have been tested to study the influence of pressure on their reaction with tetralin at the temperature of 300-320 degreesC. The coals differ strongly in reactivity with tetralin and in pressure effects. The coals with high oxygen content are the most reactive and their reaction rate was accelerated with the increase of pressure. The molar activation volume for the reaction of subbituminous coal and low-rank bituminous coal with tetralin at 300 degreesC is about - 20 and - 15 cm(3)/mol, respectively. Such results support bimolecular transition state, For high-rank bituminous coals, the reaction rate is not affected by pressure. (C) 2002 Elsevier Science B.V All rights reserved.