The intrinsic electric strength of polyvinyl alcohol has been measured at temperatures ranging from −195° C to + 90° C. At the lowest temperature, the electric strength is slightly higher than that of any other material yet measured, but it falls rapidly with increasing temperature throughout the range. Comparison of this behaviour with that of other high polymers suggests that the temperature variation of the intrinsic electric strength of these materials is determined by the dipoles present, and not by the physical structure. Lack of information on the value of the dielectric constant at low temperatures precludes exact comparison between the actual electric strength in this region and values calculated from Frohlich's formulae, but satisfactory agreement was obtained between the experimental and calculated values for polyvinyl alcohol, using the high-frequency value of the dielectric constant.