The electrodeposition of indium antimonide was investigated in a basic 1-ethyl-3-methylimidazolium chloride/tetrafluoroborate ionic liquid containing In(III) and Sb(III). Energy-dispersive spectroscopy data indicate that the composition of the In-Sb codeposits can be varied by deposition potential and concentration of In(III) and Sb(III) in the solution. At potentials where the deposition of antimony and indium is mass-transport limited, InSb compound can be obtained from solutions containing equal moles of Sb(III) and In(III). Analysis of the X-ray diffraction patterns indicates that the crystallinity of the electrodeposits is affected strongly by deposition temperature. The crystallinity of the deposits improves as the deposition temperature increases and crystalline InSb can be directly electrodeposited at 120°C. Photocurrent experiments indicate that the electrodeposited InSb was a p-type semiconductor. Infrared absorption measurements of the InSb deposits indicate a direct optical transition with an optical bandgap of 0.20 eV. © 2003 The Electrochemical Society. All rights reserved.