The dynamic mechanical behavior of a series of polycyanurate networks has been studied in the glassy state as a function of cyanate conversion, Two relaxations, beta and gamma, were defined and the Arrhenius dependence and Starkweather treatments were applied. To understand the origin of these sub-T-g relaxations, molecular modeling (both mechanics and dynamics) was used on model molecules representative of the network structure. Two types of molecular motion were examined : rotation of the phenylene ring and crankshaft of the chain segment between crosslinks (i.e., triazine rings).