Several chemical cleaning procedures for InSb͑100͒ substrates were studied. Nomarski microscopy, x-ray photoelectron spectroscopy, and Auger electron spectroscopy were used to assess their credibility for use in molecular beam epitaxial growth of high quality films. The most satisfactory substrate surface was prepared using a modified CP4A etchant ͑HNO 3 :CH 3 COOH:HF:DI H 2 O at 2:1:1:10͒. This etchant was found to produce a flat surface with low defect density and a passivating layer consisting mainly of easily removable Sb oxide.