Objectives: This review focuses on genetic and other family influences on the development of fibromyalgia syndrome [FMS] and chronic widespread pain [CWP]. We first assess the evidence concerning aggregation of pain sensitivity and psychological distress among first-degree relatives of persons with FMS, as well as the validity of the affective spectrum disorder hypothesis. We also examine several prospective, population-based studies of factors that may contribute to the onset of CWP. We conclude by reviewing current evidence concerning the relationships between specific candidate genes, the onset of FMS or other affective spectrum disorders, and pain sensitivity among persons with these conditions. © 2008 by Informa Healthcare USA, Inc. All rights reserved.