We studied 50 consecutive patients presenting at an accident department after rear-end vehicle collisions and recorded symptoms and psychological test scores within one week of injury, at three months and at two years. The range of neck movement was noted at three months. Within one week of injury, psychological test scores were normal in 82% of the group but became abnormal in 81% of the patients with intrusive or disabling symptoms at over three months (p < 0.001) and remained abnormal in 69% at two years. The clinical outcome after two years could be predicted at three months with 76% accuracy by neck stiffness, 74% by psychological score and 82% by a combination of these variables. The severity of symptoms after a whiplash injury is related both to the physical restriction of neck movement and to psychological disorder. The latter becomes established within three months of the injury.