Several properties of InSb such as high mobility and narrow bandgap make it an attractive candidate for many unique devices. We have examined the metalorganic chemical vapor deposition (MOCVD) of InSb on GaAs and InSb substrates under a variety of conditions using trimethylindium and trimethylantimony sources. The absolute metal-organic partial pressures above the susceptor were monitored using in-situ Ultraviolet (UV) absorption spectroscopy. X-ray studies of the homoepitaxial growth of InSb on InSb substrates (100) indicate good crystalline epitaxial growth while the x-ray peak for the InSb grown on GaAs (100) is broadened due to defects. Room-temperature Hall mobility measurements performed on the heteroepitaxial InSb layer on GaAs substrates indicates that the mobility of the InSb increases with increasing layer thickness. Mobilities range from 12,000 cm2/V sec for 0.8 micron layers to 38,000 cm2/V sec for 7.4 micron layers. The carrier concentrations are relatively constant (2 to 4 × 1016 cm−3 ) for the n type InSb deposited layers.