An analysis of progression of sialadenitis in patients with primary and secondary SS has been performed. For this purpose patients were prospectively followed and evaluated with respect to stimulated whole salivary secretion and morphology of labial salivary gland biopsies. Twenty-one patients with primary SS and 18 with secondary SS were followed for a mean of 39 ± 20 months (range 11–112 months). During this observation period the lymphocytic infiltration in minor salivary glands, measured as focus score, increased in 14/21 (67%) patients with primary SS and in 14/18 (78%) patients with secondary SS. Altogether there was a statistically significant increase in focus score in both primary and secondary SS, but no reduction in salivary production. Consequently, no correlation between changes in focus score and stimulated salivary secretion was found in either primary or secondary SS.