Vallejo MA, et al. - Given the significance of widespread pain for the diagnosis of fibromyalgia (FM), a Widespread Pain Index (WPI) is computed using the sum of pain regions obtained from a topographical distribution, however, there is no empirical basis for choosing the regions. Researchers here aimed at discovering an empirical distribution of the pain regions. Two hundred twenty-eight female patients with FM were administered the Fibromyalgia Survey Questionnaire, Fibromyalgia Impact Questionnaire, Combined Index of Severity in Fibromyalgia, and Short Form-36 Health Survey. They grouped the pain regions of the WPI by the topographical distribution (WPIR) and compared these with a new empirical distribution (WPIE) obtained through exploratory factor analysis. Findings revealed that compared to WPIR, WPIE has a normal distribution and shows higher correlations with FM severity. Because the right hemisphere is relatively significant in negative emotions and pain, the emotional factor is conceptualized as emotional. The decreased ability to coordinate left-right stepping could be due to physical factor.