Ten species of Phryganeidae are found in the U.K. They also occur in continental Europe and descriptions are available. Certain British larvae show distinct differences and a reassessment of some taxonomic characters is necessary. The immature stages of Agrypnetes crassicornis are described for the first time from Britain and the four Phryganea species can now be separated. Eight species have been reared through their complete life-cycle but the larvae and pupae of Agrypnia picta and Oligotricha clathrata are, still unknown in Britain. Keys are provided.