Using high-pressure liquid chromatography with diode-array ultraviolet-visible detection, we have identified benz[f]indene (C13H10) among the pyrolysis products of coal and the model compound anthracene, a three-ring compound representative of the aromatic moieties in coal. The coal pyrolysis experiments are conducted at 700-1000 degrees C in a fluidized bed reactor; the anthracene experiments, at 900-1000 degrees C in a laminar flow reactor. This is the first time that benz[f]indene has been identified as a product of either fuel, coal or anthracene. Oxidative ring rupture is proposed as the mechanism responsible for the formation of benz[f]indene and other indene benzologues in these products.