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Background and aims: Persons with chronic widespread pain (CWP) have poor medical outcomes and increased mortality. But there are no universally accepted criteria for CWP or of methods to assess it. The most common criteria come from the 1990 American College of Rheumatology (ACR) fibromyalgia (FM) criteria, but that method (WP1990) can identify CWP with as few as three pain sites, and in subjects with wide differences in illness severity. Recently, to correct WP1990 deficiencies, the 2016 fibromyalgia criteria provided a modified CWP definition (WP2016) by dividing the body into five regions of three pain sites each and requiring a minimum of four regions of pain. Although solving the geographic problem of pain distribution, the problem of just how many pain sites (pain diffuseness) are required remained a problem, as WP2016 required as few as four painful sites. To better characterize CWP, we compared four CWP definitions with respect to symmetry, extent of pain sites and association with clinical severity variables. Methods: We characterized pain in 40,960 subjects, including pain at 19 individual sites and five pain regions, and calculated the widespread pain index (WPI) and polysymptomatic distress scales (PDS) from epidemiology, primary care and rheumatology databases. We developed and evaluated a new definition for CWP, (WP2019), defined as pain in four or five regions and a pain site score of at least seven of 15 sites. We also tested a definition based on the number of painful sites (WPI >= 7). Results: In rheumatology patients, WP1990 and WPI >= 7 classified patients with <4 regions as WSP. CWP was noted in 51.3% by WP1990, 41.7% by WP2016, 37.6% of WPI >= 7 and 33.9% by WP2019. 2016 FM criteria was satisfied in WP1990 (51.1%), WP2016 (63.3%), WPI >= 7 (69.0%) and WP2019 (76.6%). WP2019 positive patients had more severe clinical symptoms compared with WP1990, WP2016 and WPI >= 7, and similar to but less than FM 2016 positive patients. In