Biodegradable poly(L-lactide-co-epsilon-caprolactone) copolymers with different L-lactide (LLA)/epsilon-caprolactone (CL) ratios of 75/25 and 50/50 were electrospun into fine fibers. The deformation behavior of the electrospun membranes with randomly oriented structures was evaluated under uniaxial tensile loading. The electrospun membrane with a higher LLA content showed a significantly higher tensile modulus but a similar maximum stress and a lower ultimate strain in comparison with the membrane with a lower LLA content. The beaded fibers that formed in the membranes caused lower tensile properties. X-ray diffraction and differential scanning calorimetry results suggested that the electrospun fine fibers developed highly oriented structures in CL-unit sequences during the electrospinning process even though the concentration was only 25 wt %. (c) 2005 Wiley Periodicals, Inc.