The thermodynamic functions, including enthalpy (H(Theta)), entropy (S(Theta)), and Gibbs free energy (G(Theta)) for 76 polybromophenazines (PBPZs) in the gaseous state at 298.15 K and 101.325 kPa, have been calculated using the density functional theory (the B3LYP/6-31G*) with the Gaussian 03 program. On the basis of these data, the isodesmic reactions were designed to calculate the standard formation heat (Delta(f)H(Theta)) and standard Gibbs energy of formation (Delta(f)G(Theta)) of PBPZs. In addition, the dependences of these thermodynamic parameters on the number and positions of bromine substitutes (N(PBS)) were discussed. It is suggested that Delta(f)H(Theta) and Delta(f)G(Theta) of PBPZs vary greatly with the substituent positions of bromine, with the influence order being position alpha > position beta, while the S(Theta) value is increased by 10 J . mol(-1) . K(-1) by increasing each bromine atom to PBPZs. It was found that when two bromines substitute in the same aromatic ring the Delta(f)H(Theta) and Delta(f)G(Theta) increase effect is ortho > meta > para. The relative stability order of PBPZ congeners was theoretically proposed based on the relative magnitude of their Delta(f)G(Theta). In addition, the values of molar heat capacity at constant pressure (C(p,m)) for PBPZ congeners have been calculated.