The recent development of a high-pressure wire-mesh pyrolysis reactor providing for the passage of a stream of sweep-gas through the sample holder - hitherto only available at atmospheric pressure - has allowed direct and reliable determinations of high-pressure pyrolysis tar yields in the relative absence of extraparticle secondary reactions. Sweeping volatiles into liquid-N-2 cooled traps has also made possible the quantitative recovery of tars for subsequent characterisation. Liquid and total volatile yields have been determined as a function of pressure, between vacuum (1.10(-5) torr) and 70 bar H,, for a set of maceral concentrates prepared from Janina (Polish) coal. Variations in liquid product structures with reaction conditions have been characterised by size exclusion chromatography, UV-fluorescence and FT-ir spectroscopy.