Within the last few years, much effort has been focused on the construction of nanoscale electronic devices incorporating nanotubes, nanowires or their crossed junctions. These include field effect transistor and single electron transistors, p-n diodes, Schottky-barrier rectifiers, and logic gates. Our work is on the study of the electrical property and the device applications of boron nanowires. Crystalline boron nanowires have been synthesized using catalyst chemical vapor deposition method. Different metals, Ti and Ni, have been used as contact electrodes to the nanowires for electrical transport study. Ni was found to be a good choice in making ohmic contact to the nanowire. Three-terminal electrical measurements illustrate p-type conduction of boron nanowires. At 4.2 K, their I-V response showed very low conductance at low bias, and beyond certain threshold, the current increases exponentially. We attribute this behavior to electrical field induced impact ionization.