Ultrafine fibers consisting of blends of polyaniline doped with p-toluene sulfonic acid and poly(L-lactic acid) were prepared by electrospinning. The presence of polyaniline resulted in fibers with diameters as thin as 100-200 rim and a significant reduction of bead formation. These fibers were visually homogeneous, and this indicated good interactions between the components of the polyaniline/poly(L-lactic acid) blend. The high interaction between the components and the rapid evaporation of the solvent during electrospinning resulted in nanofibers with a lower degree of crystallinity in comparison with cast films. The electrical conductivity of the electrospun fiber mats was lower than that of blend films produced by casting, probably because of the lower degree of crystallinity of the polyaniline dispersion and the high porosity of the nonwoven mat. This novel system opens up new and interesting opportunities for applications in biomedical devices, biodegradable materials, and sensors, among other things. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 744-753, 2009