A coaxial electrospun technique to fabricate core-shell microfibers (MFs) for drug delivery application is described. In one-step, Paclitaxel (PTX)-loaded poly(L-lactic acid-co-epsilon-caprolactone) (75:25) (P(LLA-CL) (core/shell)) was electrospun into MFs using 2,2,2-trifluoroethanol as the solvent. The physical and chemical properties of electrospun fibers were characterized by various techniques, such as scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and Fourier-transform infrared. The fiber diameter depended on both the polymer concentration and the flow ratio of PTX to P(LLA-CL). The encapsulation efficiency and ire vitro release profile were measured using high performance liquid chromatography methods. PTX released from the MFs in a short burst over 24 h followed by very slow release over the following 60 days. In addition, the cytotoxicity of PTX-loaded P(LLA-CL) MFs was evaluated using 3-[4,5dimehyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide assay on HeLa cell lines. These results indicate that PTX could be released from P(LLA-CL) fibers in a steady manner and effectively inhibit the activity of HeLa cells. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 1243-1251, 2009