Super-slow motions in the cryst. parts of poly(oxymethylene) were detected and fully characterized by the detn. of the 13C-NMR chem. shift tensor in the mol. via 2-dimensional (D) correlation of dipolar interactions and chem. shifts. The helical chains performed a screw-like rotation over +-200 Deg with activation energy of 20 +- 5 kcal/mol.