Grips and hand movements were observed during the manufacture and use of Palaeolithic tools by archaeologists. Positioning and movements of the fingers and palm were noted for each grip and activity, and regions of the hand stressed by the activities were identified. Derived morphological features in the modern human hand were assessed with regard to their contribution to the effectiveness of the grips and their potential for bolstering the hand against the accompanying internal and external forces. The potential range of effective gripping postures and movements and accompanying stresses were then estimated for fossil hominid hands. It was found that the control of most Palaeolithic stone tools requires two categories of grips. One combines passive support by the palm with movements of the stone by the thumb and fingers. Precision grips exclusively by the thumb and fingertips and a power grip that locks tools into the palm of the hand rarely occurred in the experiments, yet these are the ones usually discussed in connection with the evolution of hominid hands and tool use. The proportions and joint morphology of the <i>Australopithecus afarensis</i> hands are compatible with a variety of grips that should have facilitated habitual and effective manipulation of unmodified stones as tools. Derived human features in the Olduvai hand should have enhanced the control of stones by the thumb and fingers in the same grips. The robustness of Neanderthal hands is consistent with internal forces that are associated with intrinsic muscle control of finger position and with the large, repetitive extrinsic impulsive forces which accompany the wielding of hand-held stone tools. Previous classifications of grips are modified and extended, to facilitate communication about the evolution of hominid hand structure and function. -- AATA