The isothermal cure of a diglycidyl ether of bisphenol A with a tetrafunctional aromatic diamine has been studied in an attempt to achieve full cure (maximum glass transition temperature, Tg∞, ca. 170°C). Since high temperatures of cure are necessary for high Tg∞ systems (because of low reaction rates after vitrification), cure and thermal degradation reactions often compete. In this work Tg is used as a direct measure of conversion. An approach leading to a series of iso-Tg contours in a temperature vs. time transformation (TTT) diagram, which can be used to design time-temperature cure paths leading to particular values of Tg, is discussed.