The cyanoacetamides NCCH2CONHR1N (R2) (R3) are a new family of accelerators for the epoxy/isocyanate (EP/IC) reaction. Results obtained from systematic structure variations indicate that they belong to the “deactivated tertiary amine” type of catalyst with the cyanoacetamide group as the deactivating moiety. Reactivity can be controlled via the R1 substituent (cyanoacetamide) and/or by R2/R3. A reaction mechanism is proposed. The results of a factorial design experiment and IR determination of the oxazolidinone (OX)/isocyanurate (ICR) extinction maxima ratios were used to develope an optimized EP/IC system. A trial formulation (filled) is given in which rapid gelation, a high Tg value, and excellent mechanical properties were achieved with an accelerator concentration of less than 0.2%.