Many investigators have reported on the tolerance levels of the human head to static and impact loading. Their data are based upon investigations of loading on unembalmed and embalmed cadavers, primates and various headforms. Protective helmets are being designed, based on such data. This paper presents one of the studies in our program of investigating fatal and non-fatal motorcycle accidents from which head injury data might be derived, and a severity index could be established and collated with the studies of other investigators. We also solicit from medical examiners, neurologists, neurosurgeons, and other personnel involved in accident work to send us medical and engineering reports and helmets of well documented helmeted motorcyclist accidents. Our procedure is to conduct a program of impact loadings on helmeted instrumented headforms in an attempt to simulate the injury producing phenomena thus obtaining a measure of the forces and energies transmitted into the head.