The frequency of insurance cases following traffic accidents involving the whiplash mechanism is increasing in Norway. The economic consequences are obviously great, both for the individual patient and for society. Declarations by medical specialists may be of vital importance when assessing the degree of medical invalidity. We have investigated some of the information provided by 27 patients who were submitted for assessment of medical invalidity after traffic accidents. In eight of these cases, the information in reports from their usual doctor or physiotherapist varied from the case history described by the patient. In all these cases, a previous history of neck pain was found in the health reports, but was not mentioned, and was partly denied, by the patients. Our results underline the importance of supplementary information.