The heats of combustion at 25°C of the following solid aromatic hydrocarbons were measured in a static-bomb calorimeter: ΔH°c(biphenyl, c)=–1494.22±0.33 kcal mole–1, ΔH°c(bibenzyl, c)=–1807.24±0.26 kcal mole–1, ΔH°c(naphthalene, c)=–1232.35±0.22 kcal mole–1, ΔH°c(anthracene, c)=–1689.17±0.41 kcal mole–1, ΔH°c(phenanthrene, c)=–1686.06±0.30 kcal mole–1. These results were used to derive the heats of formation of each of the hydrocarbons. The dissociation energies of the central (C—C) bonds in biphenyl and bibenzyl were calculated to be 97.5±4.5 and 56.6±4.0 kcal mole–1, respectively.