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Except for the Kharga-Dakhla Depression in the north, Nabta Playa is probably the largest internally drained basin in the Southwestern Desert of Egypt. The center of the basin is filled with clastic materials, deposited from suspension during inundations. These finer-grained clastics interfinger with sandy beach deposits associated with early Holocene phytogenic dunes. The shores contain embedded Early Neolithic occupations ranging in age from ca. 9400 to 7250 C-14 yr B.P. (all radiocarbon ages reported in this article are uncalibrated). There was a phase of reduced sedimentation in the playa between 8100 and 7300 C-14 yr B.P. During this period, at least 130 species of plants, including 10 varieties of trees and bushes, were growing in the area. These plants may have formed a dense cover over the uplands surrounding the basin and greatly reduced the sediment load in the seasonal runoff. This was the Holocene climatic optimum at Nabta Playa. It was also the time of maximal development of human settlement in the Nubia-Sheb Pediplain. (C) 2001 John Wiley & Sons, Inc.