An acceleration sled carrying living human subjects was used to measure the dynamic response of the head and neck to —G x impact acceleration. Seated volunteers with complete pelvic and upper torso restraint were subjected to increasing impact accelerations beginning at 2.7 g and increasing in 1 g increments. The volunteers were selected to encompass the 5th to 95th percentile distribution of sitting height according to a selected reference.Precision inertial transducers were used to determine the linear and angular acceleration of the head and the first thoracic vertebra. The inertial system consisted of a biaxial accelerometer and rate gyroscope on a bite-plate, a biaxial acceierometer over the bregma, and a biaxial acceierometer and rate gyroscope over the spinous process of the first thoracic vertebra. The transducers on the bite-plate and over the bregma were rigidly connected to one another.Precision high-speed cameras were mounted on the sled to determine the displacements of the head and neck of the subject. One camera was mounted posteriorly and one mounted laterally with respect to the subject.Data handling was effected by recording the transducer outputs on analog tape, converting the analog tape to digital form, and calculating the pertinent trajectories by digital computer. The distance of test markings from a point of reference was measured from each photographic exposure and committed to punch cards in digital form. The inertial and photographic systems were completely redundant. The time reference axes of both systems were interlocked. The results obtained from both systems were compared for validation.Preliminary results are presented.