We present here the evidence for the origin of dc electrical conduction and dielectric relaxation in pristine and doped poly(3-hexylthiophene) (P3HT) films. P3HT has been synthesized and purified to obtain pristine P3HT polymer films. P3HT films are chemically doped to make conducting P3HT films with different conductivity level. Temperature (77-350 K) dependent dc conductivity (sigma(dc)) and dielectric constant (epsilon'(omega)) measurements on pristine and doped P3HT films have been conducted to evaluate dc and ac electrical conduction parameters. The relaxation frequency (f(R)) and static dielectric constant (epsilon(0)) have been estimated from dielectric constant measurements. A correlation between dc electrical conduction and dielectric relaxation data indicates that both dc and ac electrical conductions originate from the same hopping process in this system. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1047-1053, 2010