Drawing behavior, flow drawing, and neck drawing, was studied for isotacticpolypropylene fibers in CO2 laser drawing system, and the fiber structure and the mechanical properties of drawn fibers were analyzed. For a certain laser power, flow drawing of polypropylene (PP) was possible up to draw ratio (DR) 19.5. Though the drawing stress was very low, the flow-drawn PP fiber exhibited oriented crystal structure and improved mechanical properties. On the other hand, neck-drawing was accomplished from DR 4 to 12, with significant increase in drawing stress that enhanced the development of fiber structure and mechanical properties. Unlike PET, the drawing stress depends not only on the DR, but on irradiated laser power also. The 10-12 times neck-drawn fibers were highly fibrillated. The fibers having tensile strength 910 MPa, initial modulus 11 GPa, and dynamic modulus 14 GPa were obtained by single-step laser drawing system. (c) 2005 Wiley Periodicals, Inc.