Infrared and Raman spectra of poly(vinylidene chloride) (PVDC) single crystals are presented. Additionally, we report infrared spectra of a quenched, largely amorphous, sample of PVDC. Our results question the interpretation of previous vibrational studies of PVDC which conclude that the crystalline polymer chain is in the TGTG′ conformation. Strong Raman lines at 688 and 161 cm−1together with weaker lines at 3000, 345, and 143 cm−1which are either absent or, at least, extremely weak in the infrared spectrum of the crystalline polymer suggest that a planar 21helical conformation is more consistant with the vibrational data.