Constant-energy synchronous fluorescence spectroscopy was used to examine the aromatic structural features of the tars from the pyrolysis of Loy Yang brown coal in a wire-mesh reactor. Tars from the pyrolysis of the raw coal and its H-form and Ca-form coal samples at various heating rates, peak temperatures, and holding times at the peak temperature were analyzed. The synchronous spectra of all. of the tars showed two characteristic peaks with centers at ca. 335-340 and 385-390 nm. Synchronous fluorescence intensity per unit absorbance was found to be a useful parameter to examine the changes in the intramolecular energy transfer due to the changes in tar structural features. The degree of intramolecular energy transfer is considered a measure of the relative amounts of aromatic ring systems in oligomeric structures. Increasing heating rate during pyrolysis was found to enhance the release of larger (3 or more fused rings) aromatic ring systems. The introduction of ion-exchangeable cations (e.g,, Ca2+) into the brown coal suppressed the release of the larger aromatic ring systems during pyrolysis.