The present report is the fifth to be issued by this Committee in the course of 35 years' work on the petrological identification of stone implements. The four earlier reports (Keiller, Piggott and Wallis, 1941; Stone and Wallis, 1947; Stone and Wallis, 1951; Evens, Grinsell, Piggott and Wallis, 1962—hereafter referred to as the Fourth Report) were concerned primarily with stone implements from South-Western England, but also included implements from other parts of the British Isles. Since the early 1960s, when a series of regional implement petrology surveys was set up under the aegis of the Council for British Archaeology, this Committee's official work has been confined to the South-West, a region which, for administrative purposes, now comprises the seven counties of Berkshire, Cornwall, Devon, Dorset, Gloucestershire, Somerset and Wiltshire, together with the Channel Islands. Hampshire, formerly within this Committee's area of special interest, has been allocated to the South-East, with Sussex, Surrey and Kent. The present report is concerned, therefore, exclusively with implements from the South-West, as defined above.