Abnormal proteinaceous deposits identified by light microscopy as amyloid in labial salivary gland biopsies were studied by transmission electron microscopy in order to establish their ultrastructural characteristics. Results showed fine fibrils approximately 10 nm in diameter located in close relation to the basal lamina of the secretory end-pieces and ducts as well as in the interstitial connective tissue stroma of labial salivary glands; these are the typical features of amyloid. Thus, the present study confirms the light microscopy diagnosis of amyloid deposits in labial salivary gland biopsies, supporting the use of lip biopsy as a readily accessible method for the diagnosis of secondary amyloidosis.