Recently, it has become possible to measure the mobility of charges along isolated chains of conjugated polymers. The mobility of holes along poly(phenylenevinylene) and polythiophene backbones were reported to be 0.43 and 0.02 cm(2) V-1 s(-1), respectively. The large difference between the mobility of holes on poly(phenylenevinylene) and polythiophene chains can be attributed to deviations from the coplanar alignment of structural units in the polymer backbone. The effect of such torsional disorder on intramolecular hole transport is studied theoretically in this paper using a model based on the tight-binding approximation. The calculated ratio of hole mobilities along poly(phenylenevinylene) and polythiophene chains was found to be in agreement with experimental findings. For both polymers, estimated mobilities become consistent with the experimental Values if polymerization defects and chain-end effects are included in the calculations. This suggests that even higher mobilities than those reported here, can be realized by improving the effective conjugation along the polymer chain.