Chronic widespread pain (CWP) is a common symptom within the community, and may be part of or arise as a result of various diseases or conditions. Fibromyalgia (FM) is probably the most common and best known disease whose cardinal symptom is CWP. Many authors, however, indistinctively describe pain as 'widespread', 'diffuse' or 'generalised', and this may lead to misunderstandings about true clinical or scientific significance. Widespread pain has been variously defined, over the years, beginning from the American College of Rheumatology (ACR) classification criteria for FM in 1990, and the CWP Manchester definition in 1996. A comprehensive and brief core sets for CWP was developed in 2003, by the WHO International Classification of Functioning Consensus Conference, and finally, the ACR proposed new preliminary diagnostic criteria for FM in 2010. Research into CWP and/or FM is therefore difficult and can lead to conflicting results. CWP and (particularly) FM are multifactorial disorders. There is increasing evidence that they may be triggered by environmental factors, and many authors have highlighted a relationship with various infectious agents and some have suggested that vaccinations may play a role. This review analyses the available data concerning the relationships between FM and widespread pain (in its various meanings) with infections and vaccinations, from the earliest report to the most recent contributions. Considering all scientific papers, various levels of possible associations emerge. There is no clear-cut evidence of FM or CWP due to infections or vaccinations, no correlations with persistent infection, and no proven relationship between infection, antimicrobial therapies and pain improvement. A higher prevalence of FM and chronic pain has been found in patients with Lyme disease, and HIV or HCV infection, and, perhaps, also in patients with mycoplasmas, HBV, HTLV I, and parvovirus B19 infections. Some unconfirmed evidence and case reports suggest that vaccinations may trigger FM or chronic pain.