The study of the descriptive epidemiology of chronic widespread pain (CWP) in several countries is of interest, as the occurrence of this condition varies among different populations. However, reports of pain prevalence are not consensual: it is clear that chronic musculoskeletal pain is frequent all over the world, varying from 4.2% to 13.3%. The reasons for the prevalence differences in CWP might include genetic and/or environmental factors. Multifactorial aetiopathogenesis of CWP and fibromyalgia syndrome (FMS) certainly includes genetic susceptibility and environmental influences. The risk factors for the occurrence and maintenance of CWP/FMS include female gender, increasing age, family history of chronic pain, several causes of distress, obesity and poorest mental and/or physical status. On the other hand, risk factors that negatively influence the outcome of CWP/FMS are: high levels of psychological distress, presence of somatisation, presence of fatigue, poor sleep, higher number of painful sites and pain intensity, poorest mental status and functional capacity, presence of co-morbid conditions and highest number of primary-care consultations. Mild alcohol consumption and individualised social support seem to have a protective effect on the outcome of CWP/FMS.