This study describes and compares patients' reports of somatic symptoms and physicians' ratings of the same symptoms in patients with chronic non-cancer-related and cancer-related pain. Ninety-seven patients with chronic non-cancer-related pain and 100 patients with chronic cancer-related pain reported somatic symptoms using a newly developed checklist of somatic symptoms. Patients also completed the Brief Symptom Inventory-18, Courtland Emotional Control Inventory, Catastrophizing scale, two items from the Coping Strategies Questionnaire (one about efficacy to control and another about ability to decrease pain), and a numeric rating of average pain. After they completed medical histories and physical examinations on patients, physicians rated the degree to which the patients' reported somatic symptoms on the checklist were medically unexplainable. Over 80% of patients in both groups reported somatic symptoms that their physicians rated as not fully explainable. Strong associations existed between patient-reported somatic symptoms and negative mood states. For the majority of patients, results supported a concept of combined illness- and affect-related pathology rather than one of pure somatoform disorder. Assessing patients' reports of somatic symptoms and negative mood states and incorporating physicians' ratings of level of medically unexplainable somatic symptoms were useful for distinguishing these diagnoses.