Chronic pain and depression frequently occur together. A selection bias afflicts all hospital clinic and family practice populations in which this relationship has been examined. We report here some of the results from civilian populations outside institutions, examined in the United States in national surveys. The findings are based upon the recollection of individuals with respect to the period of 12 months prior to interview and upon the occurrence of depression in the previous week as indicated by the answers to the Depression Scale of the Centre for Epidemiologic Studies (CES-D). They indicate that 14.4% of the United States population between the ages of 25-74 suffer from definite chronic pain related to the joints and musculoskeletal system. Another 7.4% have some pain of uncertain duration. Eighty-three percent of the definite pain group received treatment. Chronic pain subjects scored significantly higher than normals on the CES-D (10.68 +/- S.E.M. 0.76 vs. 8.05 +/- 0.23, P less than 0.01) with subjects with pain of uncertain duration scoring similar to the definite chronic pain population (11.13 +/- 0.76). Using a high cut-off score for depression. 18% of the population with chronic pain were found to have depression. This is in contrast to 8% of the population who did not have chronic pain.