We report a study on the dielectric relaxation of polymaleimide and selected N-alkyl and N-aryl polymaleimides covering the frequency range 10 −5 to 10 6Hz and the temperature range −80° to +230°C. In most instances three relaxations are observable and these have been assigned to the glass to rubber transition, a local chain motion and an in-plane deformation of the maleimide ring. Activation energies for these processes are reported. Secondary factors such as crystallinity and, in polymaleimide and poly( N-methyl maleimide), thermal reactions are demonstrated to affect the individual relaxations.