The values of ε′ and ε″ have been measured for pure methyl, ethyl, n-propyl and n-butyl cyanides at 1.0 Mc/sec, 9.95, 20.8, and 32.0 kMc/sec. The relaxation time and the distribution parameters have been calculated from Cole-Cole plots. The value of dielectric relaxation time increases from methyl to n-butyl cyanides (3.8, 4.7, 6.2, 7.5×10—12 sec at 30°C) but the distribution parameter is decreasing with increasing chain length (0.14, 0.08, 0.02, 0.00, at 30°C). This indicates that probably there is rotation of the CN group around the C–CN bond. The cyanides are showing that the most probable enthalpies of activation are less than the corresponding free energies so that the most probable entropies of activation are negative. A recording-type dielectric measuring bench has been used for the microwave measurements.