Previous studies of anodized InSb samples cooled in the dark to 77°K have shown that initiallyn‐type surfaces are changed toptype upon visible illumination. Forn‐type bulk material an infrared photovoltaic response can be obtained from the inverted surface after such illumination. A new response has been found inn‐type samples which was present initially but which then disappeared upon visible illumination. Measurements on both types of response have shown other distinguishing features, and several models are discussed.