The relationship of the glass transition temperature, T(g), to fractional conversion, x, for the conversion of the cyclohexylmethyl ester of the benzophenone tetracarboxylic dianhydride-oxydianiline polyamic acid to polyimide has been investigated using dynamic mechanical analysis (torsion pendulum, TBA). The glass transition temperature and conversion measurements were obtained on a single solvent-free polyamic acid ester specimen during cooling after heating to successively higher cure temperatures. Conversion was determined from the intensity of a sub-T(g) mechanical relaxation peak that has been assigned to a relaxation of the cyclohexyl group. The resulting T(g) versus x relationship is nonlinear. The T(g) versus x relationship is adequately modeled using an expression derived by Couchman.