We study the coaxial spinning of poly(lactic acid) (PLA) with polypropylene (PP) in a core/sheath configuration. PPcore/PLA(sheath) and PLA(core)/PPsheath fibers maintain the high breaking strength that PP and PLA exhibit individually, showing marked improvement in strength over previous reports of PP/PLA blend fibers. Crystalline morphologies are greatly affected by the location within the fiber (i.e., core, sheath, or spun individually), and hence, co-spinning provides a route to tailor the morphology and fiber diameter beyond that available with single component fibers. A new approach to estimate molecular orientation of core sheath fibers based on the tensile response of the fiber is developed, and indicates that co-spinning PP with PIA results in a synergistic effect with increases in the molecular orientation above that which is possible with spinning either PP or PLA individually. (C) 2011 Elsevier Ltd. All rights reserved.