Proton NMR has been used to investigate interactions between a high-volatile bituminous coal and a number of aromatic hydrocarbon additives during heating at elevated temperatures. A coal-additive ratio of 4:1 was used. Coal tar pitch and aromatic hydrocarbons such as anthracene were observed to penetrate the coals at temperatures >200 degrees C and substantially increased the extent to which the coal was mobile at these temperatures. If, after the hydrocarbon had penetrated the coal, the mixture was allowed to cool to room temperature and then was reheated, the extent to which the mixture was mobile was substantially altered. The extent to which the reheated mixture was mobile at 100 degrees C decreased with both increasing molecular weight and increasing polarity of the additive but was not dependent on the melting point of the additive. Studies using deuterated anthracene showed that the coal in these reheated mixtures itself started to become significantly mobile at similar to 150 degrees C, that is, at temperatures at which neither coal nor anthracene alone was mobile. These results are interpreted in terms of a general interaction between the coal and the hydrocarbons that is probably electrodynamic in nature.