Objective: To determine the relationship between physically traumatic events and the onset of chronic widespread pain (CWP). Methods: This was a case-control study nested within a large prospective cohort. CWP was determined, by questionnaire, as per the American College of Rheumatology fibromyalgia classification criteria. Data were also collected on psychological health, health behavior, and sleep problems. Participants without CWP were then followed up at 4 years, and (new-onset) CWP was determined in the same manner. At followup, participants were also asked to report whether they had experienced any of a series of physically traumatic events between baseline and followup. Results: A total of 2,069 individuals (46.6%) participated at followup, and 241 of these individuals (11.6%) reported CWP. More than one-third of the study population reported at least 1 physically traumatic event; although these individuals were more likely to develop CWP, this relationship was completely attenuated after adjustment for confounding (odds ratio 1.01, 95% confidence interval 0.73-1.40). However, there was some evidence to suggest that involvement in a road traffic accident, specifically, may confer an increase in the risk of CWP onset. Conclusion: This study provides support for the "at risk" phenotype hypothesis, where individuals characterized by poorer health and psychological variables may be predisposed to develop CWP following a traumatic trigger. However, although this has been seen with road traffic accidents, it is not the case with other events. Future research should examine what is peculiar about an accident, or about one's reaction to it, that confers this increase in the risk of CWP onset. © 2011, American College of Rheumatology.