Differential scanning calorimetry (d.s.c.) has been applied to characterize the miscibility of blends of a high T(g) polyester, synthesized by condensation polymerization from 4,4’-(2-norbornylidene)diphenol and terephthalic acid/azelaic acid in a 60/40 molar ratio (this polyester will be denoted T(40)C-GJ), with bisphenol-A polycarbonate. The theoretical development to determine the Flory-Huggins interaction parameter (chi) of phase-separated polymer blends from their phase compositions is described. The glass transition temperature (T(g)) of a miscible blend of T(40)C-GJ and a low molecular weight polycarbonate (Lexan) can be accurately described by both the Gordon-Taylor equation with k = 1.7 and the Couchman equation. These equations were used to determine the phase compositions of a phase-separated blend of T(40)C-GJ and a high molecular weight polycarbonate (Makrolon) from the T(g) data. The chi values for these blends are in the range (8.4-9.9) x 10(-3) and are slightly composition dependent. The miscibility of these blends can be quantitatively understood in terms of the chi results from the d.s.c. measurements. The morphology observed by transmission electron microscopy for 50/50 wt% blends of T(40)C-GJ and polycarbonate is consistent with the d.s.c. results.