The application of semiconductor devices to the detection and analysis of gamma ray, X-ray and nuclear radiations is outlined. After a brief discussion on semiconductor detector principles, including mode of operation, choice of material and energy resolution various types of semiconductor detector are described. The uses of semiconductor devices in the fields of nuclear particle counting and spectrometry, gamma spectrometry, space physics, medical physics and energy dispersive X-ray spectrometry are discussed. Despite the great importance of processing the detected signal, only brief mention is made of the electronic techniques used, emphasis being on the detecting devices themselves.