Conducting polythiophene (PTh)/single-wall carbon nanotubes (SWNTs) composites were synthesized by the in situ chemical oxidative polymerization method. The resulting cablelike morphology of the composite (SWNT-PTh) structures was characterized with elemental analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared, ultraviolet-visible spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and transmission electron microscopy. The standard four-point-probe method was used to measure the conductivity of the samples. Field emission scanning electron microscopy and transmission electron microscopy analysis revealed that the SWNT-PTh composites were core (SWNTs) and shell (PTh) hybrid structures. Spectroscopic analysis data for the composites were almost identical to those for PTh, supporting the idea that SWNTs served as templates in the formation of a coaxial nanostructure for the composites. The physical properties of the composites were measured and also showed that the SWNTs were modified by conducting PTh with an enhancement of various properties. (c) 2006 Wiley Periodicals, Inc.