We studied the prevalence of fibromyalgia in 3 different groups of patients affected respectively with systemic lupus erythematosus, systemic sclerosis (scleroderma) and primary Sjögren's syndrome. The typical fibromyalgia findings encountered in these diseases were examined.We enrolled 250 consecutive outpatients: 100 with systemic lupus erythematosus, 50 with systemic sclerosis, 100 with primary Sjögren's syndrome and 2 control groups (30 healthy subjects and 75 patients with primary fibromyalgia). Fibromyalgia features were evaluated by algometry, VAS for pain, Mc Gill Pain Questionnaire and Fibromyalgia Impact Questionnaire.Fibromyalgia has been found in 1 case (1%) with systemic lupus erythematosus, 1 case with systemic sclerosis (2%), 22 cases (22%) with primary Sjögren's syndrome and in 1 (3.3%) of the healthy controls. The number of tender points was significantly higher (p<0.01) in the patients with Sjögren's syndrome in comparison with the other groups. Fibromyalgic findings were similar in the patients with primary fibromyalgia and Sjögren's syndrome with fibromyalgia, unless for both poor sleep and low algometric thresholds which were more frequently found in primary fibromyalgia (respectively p<0.001 and p=0.05).Our study suggests that fibromyalgia is relatively frequent in primary Sjögren's syndrome, while in systemic lupus and systemic sclerosis its prevalence is not different from that found in the healthy controls. Typical fibromyalgia findings, except algometric values, were similar between the cases with Sjögren's syndrome plus fibromyalgia and fibromyalgia alone.