Fatigue and generalised pain are debilitating symptoms that negatively impact the quality of life in patients with systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS). Chronic widespread musculoskeletal pain and fatigue are the clinical hallmarks of fibromyalgia (FM), a clinical entity which can be associated to connective tissue disease. The aim of the present study was to assess the prevalence of FM syndrome, fatigue and widespread pain in SLE and pSS patients and to evaluate the contribution of inflammatory disease and FM on those constitutional symptoms. Fifty SLE and 50 pSS patients were enrolled in the study. Patients rated fatigue, pain, and disease activity using a 100-mm visual analogue scale and completed the Health Assessment Questionnaire and the Fibromyalgia Impact Questionnaire. Zung depression and anxiety scales were used to quantify mood disorders. Tender points were evaluated using an algometer. Disease activity score as evaluated for each SLE and pSS patient. Fibromyalgia has been diagnosed in a significantly higher percentage of SLE patients than pSS patients (32% vs. 18%, p=0.022) even if the percentage of patients reporting fatigue and pain was higher among pSS patients. No correlation with disease activity was observed in either group of patients. FM seems to contribute to constitutional symptoms more in SLE than in pSS, suggesting a different underlying cause of fatigue and widespread pain in these two different connective tissue diseases.