Lysozyme and total protein concentrations in parotid saliva were measured in 17 patients with primary Sjögren's syndrome, in six patients with Sjögren's syndrome secondary to hyperlipoproteinemia and in 14 age- and sex-matched healthy control subjects. Increased lysozyme concentrations were found only in patients with primary Sjögren's syndrome and correlated well with the presence of parotid gland enlargement. The total protein concentration in the saliva of patients with Sjögren's syndrome was not different from that of the control subjects. Parotid saliva lysozyme determination may be useful as an early adjunctive diagnostic test of primary Sjögren's syndrome.