We measured salivary beta2 microglobulin concentrations in 49 patients evaluated for Sjögren's syndrome with a labial salivary-gland biopsy. The salivary concentration was elevated and a significant correlation (P less than 0.001) was found between the concentration and the degree of inflammation seen in the biopsy. Serum concentrations were increased in 135 patients with Sjögren's syndrome. Striking elevations were seen in patients with associated renal or lymphoproliferative complications. Three patients have an increase in serum beta2 microglobulin concentration in association with exacerbation of their disease, and six a decrease after clinically efficacious therapy. These data indicate that determination of beta2 microglobulin in saiva may provide a simple, noninvasive technic for estimation of the degree of local inflammation in autoimmune disease.