Polyoxymethylene (Delrin) was shown by 13C-NMR and relaxation time (45 MHz with proton-decoupled, magic-angle spinning, with and without cross polarization) to contain a cryst. phase with short rotating-frame spin-lattice relaxation time (Tlr) and long spin-lattice relaxation time (Tl), and an amorphous phase with a longer Tlr and a shorter Tl. The cryst. Tlr, which is detd. by spin-spin interaction as well as spin-lattice relaxation, depends on the spinning frequency. At spinning rates >5 kHz, the line width under magic-angle spinning conditions increases with increasing spinning rate.