Dielectric losses in polyacrylonitrile (PAN) and three pyrolyzates were studied between 1 Hz. and 300 kHz. Pure PAN has at 20°C. a very broad loss region with a maximum at 70 Hz. which is ascribed to CN groups. Powdered PAN was pyrolyzed in a nitrogen atmosphere at 170, 220, and 300°C. PAN-170 has the same loss maximum as the unpyrolyzed polymer, but the maximum had disappeared in PAN-220. This is attributed to formation of conjugated chains by linking of CN groups above 200°C. However, this does not enhance the conductivity until hydrogen is eliminated above 350°C.