BACKGROUND: Identified aetiological factors for chronic widespread pain (CWP) are largely related to emotional and behavioural factors, but current management leads to modest improvement in symptoms. Vitamin D deficiency has been suggested as a new modifiable risk factor for CWP. OBJECTIVE: To examine the association between vitamin D status (measured by 25-hydroxyvitamin D (25(OH)D)) and CWP in a nationwide population sample of white British adults, accounting for potential mediating and confounding lifestyle factors. METHODS: 9377 participants born 1 week in March 1958, in England, Scotland or Wales and completing a biomedical assessment at age 45; 6824 eligible participants had data on 25(OH)D and completed pain manikins. RESULTS: Prevalence of CWP varied by 25(OH)D concentration in women but not in men, with the lowest prevalence observed for women with 75-99 nmol/l (14.4% for <25 nmol/l, 14.8% for 25-49 nmol/l, 11.6% for 50-74 nmo/l, 8.2% for 75-99 nmol/l and 9.8% for participants with > or =100 nmol/l). There was an interaction between 25(OH)D concentration and gender in relation to CWP (interaction, p = 0.006), which was not fully explained by differences in lifestyle or social factors (adjusted interaction, p = 0.03). For women, the association between 25(OH)D concentration and CWP persisted after full adjustment (odds ratio (OR) for <75 nmol/l vs 75-99 nmol/l 1.57, 95% CI 1.09 to 2.26), while no evidence for an association was apparent in men (OR = 1.03, 95% CI 0.75 to 1.43). CONCLUSION: Current vitamin D status was associated with CWP in women but not in men. Follow-up studies are needed to evaluate whether higher vitamin D intake might have beneficial effects on the risk of CWP.