We studied the natural history and prognostic factors in 100 patients who had sustained neck sprains in rear impact road traffic accidents, and who had all originally been seen for medicolegal reports. They were seen for clinical and radiological review at a mean of 8 years after injury. The detailed medicolegal reports from the early years were available on all patients, and were used to supplement the information obtained at review. Of the patients, 50 per cent had significant pain at 8 months, decreasing to 22 per cent at 2 years and 18 per cent at 3 years. At review, 45 per cent were free of pain, and 14 per cent had significant pain. Front seat position, pain within 12 h of injury, past history of neck pain and degenerative changes on radiographs were associated with a longer duration of significant pain (P < 0.05). Early onset of pain was also associated with a worse level of pain at review. The timing of compensation was not associated with improvement in symptoms. The injury had not accelerated the development of degenerative changes.