Three vitrinite-rich coals, two South African and one Polish, were examined. In all three cases collotellinite dominated over other macerals. The detailed microscopic observations revealed a close relationship between this maceral and slitted particles known as pseudovitrinite. To test the carbonizing ability of pseudovitrinite, two coking coals and one highly volatile coal (a component in coking blends) were chosen. They were subjected to heating conditions in an inert atmosphere at 350 degrees C, 450 degrees C and 800 degrees C. The products obtained were subsequently microscopically analysed and the following observations were made: (i) at 350 degrees C: the amount of slitted particles increased dramatically in all three samples. An increase in the reflectance of both vitrinite and pseudovitrinite was also observed, the latter being visibly higher than that of vitrinite; (ii) at 450 degrees C the reflectance of both components became equal and in coking coals several slitted particles of pseudovitrinite displayed a mosaic pattern; and (iii) at 800 degrees C there was no evidence of slits and inert fragments identified in the coke were exclusively of inertinite origin. It was concluded that, at least in the samples analysed, pseudovitrinite is reactive under the given coking conditions. The increased pseudovitrinite content in coals heated to 350 degrees C indicates that part of this component (cryptopseudovitrinite) is difficult to identify during routine maceral analysis.