Injury of the neck may result when a motor vehicle is run into from behind; such injury is frequently the cause of prolonged disability and litigation. We report a series of 61 patients with these injuries. A classification, based upon the presenting symptoms and physical signs has been evolved. This classification is shown to be a reliable basis for formulating a prognosis. Factors which adversely affect prognosis include the presence of objective neurological signs, stiffness of the neck, muscle spasm, and pre-existing degenerative spondylosis.