<p>Xerostomia (dry mouth) is induced by various causes and relatively difficult to diagnose and treat properly. Although salivation-promoting agents, such as pilocarpine and cevimeline hydrochlorides, have been developed and clinically available, these effects are limited and only symptomatic for the disease status with salivary gland damages. The representatives are Sjögren's syndrome (SS) and IgG4-related disease (IgG4-RD). At this presentation, I will focus on the pathogenesis of these two diseases and possible therapeutic strategies for them.</p><p>SS is a well-known autoimmune disease and induce tissue damages specifically in exocrine glands such as salivary and lacrimal glands. In contrast, IgG4-RD is currently recognized as a novel systemic disease entity characterized by elevated levels of serum IgG4 concentration and tumefaction or tissue infiltration by IgG4-positive plasma cells, and includes autoimmune pancreatitis, sclerosing cholangitis, tubulointerstitial nephritis, retroperitoneal fibrosis, Riedel's thyroiditis, and so on. So-called Mikuliçz's disease has been reported to share these unique features, and is thus specially called IgG4-related dacryoadenitis and sialoadenitis (IgG4-DS). Although IgG4-RD shows some similar pathological features to those of SS, differences in clinical, pathological, and immunological features among these two diseases have been identified. Finally, curative therapeutic strategies based on pathology of these diseases will be discussed.</p>