A single-blinded controlled trial was conducted to test the efficacy of low-dose oral human interferon-alpha (IFN-alpha) to improve salivary function in patients with Sjögren's syndrome. Fifty-six outpatients with primary and 4 patients with secondary Sjögren's syndrome were assigned randomly into treatment groups of either IFN-alpha or sucralfate (control). The IFN-alpha (150 IU) or sucralfate (250 mg) was given orally three times a day for 6 months. Saliva was quantitated monthly by the Saxon test. After 6 months of treatment, 15 of 30 (50%) IFN-alpha-treated patients had saliva production increases at least 100% above baseline, whereas only 1 of 30 (3.3%) sucralfate patients had a comparable increase (p < 0.001). The increase in saliva production, by treatment group, was significantly greater (p < 0.01) in the IFN-alpha treated group at every month after treatment. Serial labial salivary gland biopsies of 9 IFN-alpha responder patients showed that lymphocytic infiltration was significantly decreased (p < 0.02) and the proportion of intact salivary gland tissue was significantly increased (p = 0.004) after the IFN-alpha treatment. In this study, IFN-alpha therapy significantly improved Sjögren's syndrome salivary gland dysfunction.