AlxGa1−xN alloys are very attractive materials for application to ultraviolet photodetection. AlGaN photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes, p–n junction photodetectors and phototransistors have been recently developed. In this work we analyse the performance of AlGaN-based photodetectors, discussing present achievements, and comparing the characteristics of the various photodetector structures developed to date.