The gas transport properties of a series of polyarylates based on isophthalic acid have been examined. The polyarylates were synthesized from the following bisphenol monomers with and without tetrabromo substitution : bisphenol A, hexafluorobisphenol A, phenolphthalein, and fluorene bisphenol, to study the effects of tetrabromination in combination with varying the bisphenol connector group size and shape. Substitution of a tertiary butyl group at position five on the isophthalate ring was used to increase polymer permeability. Tetra-bromination of the bisphenol maintains or increases gas permeability and significantly increases permselectivity particularly for the O-2/N-2, gas pair as compared with the nonbrominated analog. The substitution of t-butyl groups increases gas permeability by two-to fourfold but lowers permselectivity. Most of the increase in permeability can be related to an increase in the diffusion coefficient for each gas. All the brominated polyarylates have gas transport properties superior to most known glassy materials for O-2/N-2 separation with several materials close to a proposed empirical "upper bound" between permeability and selectivity.