At Olduvai Gorge natural erosion exposed a deep series of superimposed geological beds containing rich artefact and fossil assemblages spanning the last 1.8 million years. The sire ot famous as a rsult of excavations conducted there since 1951 under the direction of Mary Leakey and her husband, the late Louis Leakey. This volume, written largely by Mary Leakey herself, is the last of the reports and records the archaeological finds in the upper part of the Olduvai sequence from excavations carried out from the end of 1968 until 1971. The period covered here is from about 1.2 to 0.4 million years ago and th efinds include artefacts and faunal remains excavated from sites in beds II, IV na the Masek beds. The volume follows on from the archaeological record in beds I and II published in volume 3 of the series.