The noncubic II–V semiconductors have been studied recently by several workers. A review will be given of the present situation. The energy gaps of these materials range from 0.13 to over 1 ev. Room temperature mobilities of 10–15 000 cm2/v sec have been observed. Anisotropy of electrical and optical properties have been reported for several of the compounds. For CdAs2it has been possible to explain the anisotropy of Hall mobility by a simple energy band model.