Previously reported measurements on the high dielectric constant polymer, cyanoethylcellulose, (C. W. Lewis and D. H. Hogle, J. Polymer Science 21, 411 (1956).) have been extended to a wide temperature range with material of three different degrees of substitution. Dielectric data from −76°C to 150°C over a frequency range from 25 cycles to 45 megacycles has been obtained from mono-(6.5% N), di-(10.4%) N), and “tri”-(12.6% N) cyanoethylated cellulose. The dielectric constant and dissipation factor variation with frequency is illustrated in Figures 1 and 2 for two temperatures. Dissipation factor data for cellulose (cellophane), by Stoops, (J. Am. Chem. Soc. 56, 1480 (1934.) as plotted in Figure 2 illustrates a relaxation time for the OH dipole in cellulose of the same order of magnitude as for the cyanodipole in the cyanoethylated compound.