A nylon 6 microfiber was easily obtained through carbon dioxide laser heating. The laser heating was carried out in two steps: the first laser heating was performed under an applied tension of 36.7 MPa at a power density of 17.3 W cm(-2), and the second was performed under 0.18 MPa at 51.81 W cm(-2). The microfiber was obtained by the second laser heating of the fiber. The microfiber prepared under the optimum thinning conditions had a diameter of 1.9 mum and a birefringence of 46.2 x 10(-3). Its draw ratio, estimated from the diameter, was 9895x (so far, it has been impossible to achieve such a high draw ratio by drawing). A (200) reflection and a (002/202) doublet due to an a form were observed on the equator, but no (200) reflection due to a gamma form was observed. The morphology of the crystallites existing in the microfiber was only the a form. Laser heating made the microfiber more easily than conventional technologies, such as conjugate spinning, melt blowing, and flash spinning. (C) 2004 Wiley Periodicals, Inc.