The value of sialochemistry in the study of Sjögren's syndrome was explored by comparative examination of a spectrum of parotid components in twelve subjects with a positive diagnosis of the disease and twelve control subjects with normal gland function. The subjects with Sjögren's syndrome all exhibited a marked reduction in flow rate and phosphate concentration and a marked elevation in sodium and chloride concentration. The concentration of IgA was somewhat elevated (commensurate with reduced flow rate); the levels of IgG, IgM, and albumin were normal. The major functional abnormality in the parotid gland in Sjögren's syndrome appears to be luminal transport in the ductal region; leakage of serum components is minimal. Sialochemistry can be helpful in differentiating Sjögren's disease from other diseases of the salivary gland and in assessing degree of pathologic change.