The salivary glands are integrated into the body in such a complex manner that the analysis of the saliva allows conclusions about pathological function of other organ systems. Such interactions between salivary glands and the body as a whole play an important role in the etiology and pathogenesis of the different types of sialadenitis. An etiological classification is a proven method for arriving at a clinical diagnosis. Etiological factors include traumas, bacteria, viruses, ductal obstructions, disturbances of secretion, radiogenic damage, and immunological reactions (immunocomplex, tuberculin, or autoimmune types). Frequently the etiology is influenced by several factors. After a brief discussion of the clinical diagnostic methods, we present the clinical and morphological findings concerning the various types of sialadenitis and their differential diagnosis.