This is the fifth in a series of fasicules publishing tne British Museum's programme of research excavations at Grimes Graves, Norfolk. It provides an account of the exploration of the deep mine sites which formed one component of a reassesment of how the mine field itself developed. A reapraisal of some previously examined pits is incorporated, along with a catalogue of other shafts known to have been excavated or partisally explored, including hitherto unpublished data. A final section assesses the original mining methods used and the quantity of flints likely to have been excavated.