The tables in our first two papers on polycyclic aromatic hydrocarbons [J. Phys. Chem. Ref. Data 17, 241 (1988) and J. Phys. Chem. Ref. Data (18, 77 (1989)], have been extended by calculating thermodynamic properties for the first two isomer groups in the naphthocoronene series, the first two isomer groups in the ovalene series, and first members of some higher series. Successive isomer groups in each series differ by C4H2. The properties of individual species have been estimated using Benson group values of Stein and Fahr for temperatures from 298.15 to 3000 K. Values of C° p, S°, ÎfH°, and ÎfG° for a standard state pressure of 1 bar are given for isomer groups and for individual species. The isomer group values provide a basis for extrapolating to higher carbon numbers where it is not feasible to consider individual molecular species. © 1990, American Institute of Physics for the National Institute of Standards and Technology. All rights reserved.