Self-assembled micro/nanotubes (650-76 nm in diameter) of polyaniline (PANI) were synthesized in the presence of beta-naphthalene sulfonic acid (beta-NSA) as a dopant. It was found that the diameter and room-temperature conductivity of the PANI-NSA tubes decreased with the decrease of the molar ratio of beta-NSA to aniline. On the bases of the results obtained from X-ray diffraction (XRD) and dynamic lighting scattering (DLS), it was proposed that when the molar ratio of beta-NSA to aniline was high (e.g. 2), the NSA-An salt precipitate formed by beta-NSA and aniline played a "template-like" role in forming the PANI-NSA tubes, while the "template-like" role was played by the NSA-An micelle when the ratio is low (e.g., 1/2 or 1/4).