The carrier transport of carefully purified regioregular poly(3-hexylthiophene) films has been studied using time-of-flight photocurrent measurements. We find balanced ambipolar transport with a room-temperature mobility for holes of 3×10-4 cm2 V-1 s-1 and for electrons of 1.5×10-4 cm2 V-1 s-1 at electric fields ≥105 V/cm. The transport is relatively field independent and weakly temperature dependent, pointing to a high degree of chemical regioregularity and purity. These factors make poly(3-hexylthiophene) attractive for use in a range of electronic applications. © 2004 American Institute of Physics.