This paper outlines the clinical, serologic, and immunogenetic differences and similarities of Sjögren's syndrome alone (primary) and Sjögren's syndrome associated with rheumatoid arthritis and systemic lupus erythematosus (secondary). The immunoregulation in Sjögren's syndrome is discussed and the incidence of immune complex-like material, its nature, pathophysiology, and clearance by the Fc receptor of the reticuloendothelial system presented.