A zone-drawing and zone-annealing method was applied to a poly(ethylene terephthalate) microfiber, obtained by using CO2 laser thinning, to develop its mechanical properties. The microfiber used for the zone drawing and zone annealing was prepared by winding at 1386 m/min the microfiber obtained by irradiating the laser at 18.1 W/cm(2) and had a diameter of 2.8 mum and a birefringence of 0.097. Zone drawing was carried out at a drawing temperature of 105degreesC under an applied tension of 53 MPa, and zone annealing at an annealing temperature of 155degreesC under 195 MPa applied tension. Zone drawing and zone annealing were carried out at a treatment speed of 0.21 m/min. The diameter of the microfiber decreased, and its birefringence increased, with zone drawing and zone annealing. The zone-annealed microfiber finally obtained had a diameter of 2 mum, a birefringence of 0.234, a tensile modulus of 17.9 GPa, and a tensile strength of 1.1 GPa. The wide-angle X-ray diffraction photograph of the zone-annealed microfiber showed the existence of highly oriented crystallites. (C) 2004 Wiley Periodicals, Inc.