Theoretical predictions suggest that the thermoelectric properties of nanowires will be enhanced significantly compared with bulk materials. 1 However, since a single nanowire does not have a high enough conductivity to be useful in most applications, it is necessary to use a template to organize a large collection of nanowires. 2 While there have been reports of the preparation of single nanowires of high quality, it is more challenging to fabricate arrays with a high density of nanowires ( >5 × 1010 nanowires/ cm2) over a large area ( >1 cm2). As a step toward applying 1D thermoelectric materials, we have synthesized 40 nm diameter wires of Bi2Te3 in porous alumina templates. Bulk doped Bi 2Te3 is currently the most efficient thermoelectric material at 25°C, and a good target material for thermoelectric nanowires. Prior work has shown that high-quality films of Bi2Te3 can be deposited directly by electrochemical reduction of Bi3+ and HTeO2 in acidic aqueous solutions. 3 Wires with a diameter of∼250 nm have also been prepared by attaching a porous alumina template to a conducting material and confining the growth to within the pores. 4 Since the deposition occurs by electron transfer from the surface of the conducting material, the wires nucleate at the bottom of the pores and grow continuously up the pore. The fact that continuous wires are obtained is a key advantage of electrodeposition, particularly for applications in which conductivity is important (e.g., thermoelectric devices). In addition, porous alumina is a good choice for a template because the pore diameters are easily adjusted (down to 9 nm) to sizes enabling quantum confinement. Moreover, the pore densities ( ∼7 × 1010 pores/cm2) and aspect ratios (up to 100 μm long) are high. 5