Multi-hollowed fibers with a hollowness ratio of over 20% were successfully produced using a neck-drawing technique accompanied by CO2 laser irradiation on unoriented and amorphous polytrimethylene terephthalate (PTT) fibers with diameters of approximately 104 mm. The structure and mechanical properties of the multi-hollowed fibers were characterized using scanning electron microscopy, wide angle X-ray diffraction (WAXD), birefringence measurements, and tensile tests. Crystal orientation factors in the direction normal to the (010) and (002) planes, which were obtained from WAXD patterns, were lower in comparison to values obtained in previous studies on fibers that did not feature these hollows [9] because of the development of these internal hollows. The PTT fibers in this study also displayed high toughness, about 465 MPa (3.5 cN/dtex) strength and about 40% elongation, and had excellent elastic recovery (>95%) after 10 stretch cycles. (C) 2015 Society of Plastics Engineers