MgB2 nanowires were synthesized on various kinds of substrates by chemical vapor transportation reaction and solid state reaction. The morphology examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) shows that the diameter and the length of the nanowires are approximately 50 nm and hundreds mu m, respectively. The FFT pattern of the high-resolution transmission electron microscopy (HRTEM) image of MgB2 illustrates that the nanowire has quasi-single crystal hexagonal structure. The low DC field magnetic response displays a perfect diamagnetism with onset superconducting transition temperature of 35 K. The superconducting hysteresis loop measurement indicates that the critical current density decreases with increasing applied magnetic field. (c) 2007 Elsevier B:V. All rights reserved.