Ten cases of chronic nonspecific sialadenitis of the parotid and submandibular glands were studied by a combination of immunohistochemistry (to detect cytoplasmic filaments), morphometry, and electron microscopy in order to assess histological modifications that might reflect on the concepts for the induction of neoplasia in these glands. Histologically, the gradual atrophy of the glandular parenchyma results in the presence of many small ductules. Although structural alterations were apparent at all levels of the secretory/excretory glandular components, and in all types of cells, the fact that many such ductules resulted from gradual dedifferentiation of acinar cells was a major finding. The results suggest that no cell-type in salivary gland can be excluded as having a potential for neoplastic transformation and that the basis for the currently held reserve cell hypothesis is likely incorrect.