High-speed cinematograph films of a drilling woodpecker were examined by direct visual inspection and by a microdensitometer and computer-imaging technique. These showed (1) that the drilling trajectory is essentially linear, with very little, if any, rotation of the head; (2) that there is minimal movement after impact; (3) that the impact velocity is of the order of 600 to 700 cm/s; and (4) that the impact deceleration is of the order of 1,000 g. Dynamic and morphologic findings in the woodpecker may be highly relevant to the prevention of concussion and brain injury in man. Taken in the context of modern packaging technology and other animal and mathematical modelling research, they suggest that brain injury preventive systems could be greatly improved over those now in common use.