The phase structures of a series of ethylene-dimethylaminoethyl methacrylate (EDAM) copolymer samples were investigated by solid-state high-resolution C-13 n.m.r. spectroscopy. It is found that at least the alpha and beta methylene units relative to the tertiary carbon of dimethylaminoethyl methacrylate (DAM) along the molecular chain as well as DAM comonomer units are located outside the crystalline region. The C-13 CP-MAS spectra also reveal that with increasing DAM content, the ratio of monoclinic to orthorhombic crystals increases as well as the ratio of interfacial to crystalline regions.