We have employed molecular beam epitaxy in the growth of InSb on GaAs and InP. The transport, optical and structural properties of the films were investigated by in-situ reflection high energy electron diffraction, Hall effect and temperature dependent Hall effect, photoluminescence, transmission electron microscopy and X-ray diffractometry techniques. We report mobilities of up to 32,000 cm2/volt-sec and free electron concentrations of 3x1016/cm3 at room temperature. We have discovered a new defect state in InSb with an energy position of Ec - 0.05 ± 0.006eV. Optical and structural measurements reveal that the differences in thermal expansion and lattice mismatch between the substrates and films results in the broadening of the X-ray diffraction peaks and the near gap photoluminescence linewidths. Furthermore, we observe band gap shifts to higher energies of 10meV and 20meV for growth on GaAs and InP, respectively.