Abstract The standard massic energies of combustion of eight polycyclic compounds were measured atT=298.15 K by static-bomb combustion calorimetry. The standard enthalpies of vaporization and sublimation were measured in a Calvet microcalorimeter, or adiabatic vaporization calorimeter, or derived from ebulliometric measurements of the vapour pressure as a function of temperature. The standard molar enthalpies of formation in the condensed and gaseous states were obtained from these data. The peculiarities in the strain energies of polycyclic compounds are discussed.