Nanofibers of Poly(styrene-β-isobutylene-β-stryrene) (SIBS) and single-wall carbon nanotubes (SWNT) were prepared using electrospinning. The electrospun fiber webs consisted of an interconnected microporous structure that have potential advantages of enhanced mass transport and provision of interpenetrating 3D networks for cell attachment and proliferation. Solution conductivity, surface tension, and viscosity were the key parameters in determining the suitability of polymer solutions for electrospinning. Scanning electron microscopy (SEM) images showed that few fibers were obtained when the concentration of SIBS was less than 7% (w/v) in the dispersion. The presence of SWNTs through the electrospun fibers rendered the composite fibers conductive and electroactive. This useful combination of properties, combined with the compatibility of the SIBS/SWNT fibers with L-929 cells, are further used as substrates for studies of the effects of electrical stimulation.