The molecular morphology and the local dynamics of a series of aromatic terpolyesters based on p-hydroxybenzoic acid, hydroquinone, and isophthalic acid were investigated using X-ray diffraction and high-resolution solid-state C-13 NMR. Correlations between the existence of well-defined crystalline forms and the local mobility of the individual polymer units were established. In certain cases, polymers containing less than 30% p-hydroxybenzoic acid exhibit a crystalline reorganization upon annealing, giving rise to a change in the dominant crystalline form. The C-13 chemical shift tensor parameters were determined from the spinning sideband intensities for the polymers containing 27 and 80% p-hydroxybenzoic acid. Depending on the temperature, two types of molecular motions were observed for the para-substituted phenyl rings. At low temperatures, there first occur ring oscillations around the para axis; then, at higher temperatures, small-amplitude main-chain reorientations are involved in the glass transition phenomena. In addition to these findings, a postcondensation with an attendant increase in molecular weight was detected under annealing for these polymers.