Diodes within individual silicon nanowires were fabricated by doping them during growth to produce p-n junctions. Electron beam lithography was then employed to contact p- and n-doped ends of these nanowires. The current-voltage (I-V) measurements showed diode-like characteristics with a typical threshold voltage (Vt) of about 1 V and an ideality factor (n) of about 3.6 in the quasi-neutral region. The reverse bias I-V measurement showed an exponential behavior, indicating tunneling as the current leakage mechanism.