A standardized sleep questionnaire was used to investigate the sleeping habits of outpatients with primary Sjögren's syndrome (pSS) (n = 40) and RA (n = 42). Sleep deficit (difference between need of sleep and actual sleeping time) was significantly higher in patients with pSS when compared with healthy matched controls (PPPPPn = 10) had some sleep disturbances; reduced sleep efficiency (n = 8), increased number of awakenings (n = 5) and increased wakefulness surrounded by sleep (n = 9). Five patients had alpha intrusion in their sleep EEGs. The sleep disturbances seen in patients with primary Sjögren's syndrome may contribute to the fatigue associated with this disease.