It is widely accepted that psychosocial factors are related to illness behaviour and there is some evidence that they may influence the rate of recovery from post-traumatic disorders. The abilities of psychosocial stress, somatic symptoms, and subjectively assessed cognitive impairment to predict delayed recovery from common whiplash were investigated in a follow-up study. 78 consecutive patients referred 7.2 (SD 4.5) days after they had sustained common whiplash in car accidents were assessed for psychosocial stress, negative affectivity, personality traits, somatic complaints, and cognitive impairment by semistructured interview and by several standardised tests. On examination 6 months later 57 patients were fully recovered and 21 had persisting symptoms. The groups' scores for the independent variables assessed at the baseline examination were compared. Stepwise regression analysis showed that psychosocial factors, negative affectivity, and personality traits were not significant in predicting the outcome. However, initial neck pain intensity, injury-related cognitive impairment, and age were significant factors predicting illness behaviour. This study, which was based on a random sample and which considered many other possible predictive factors as well as psychosocial status, does not support previous findings that psychosocial factors predict illness behaviour in post-trauma patients.