Transforming growth factor beta (TGFβ) is a secreted protein present in the circulation and is a critical regulator of the body's immune system. TGFβ is believed to control several components of the immune system and inhibit autoimmune reactions. Systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS) are prototypical human autoimmune diseases characterized by the circulating autoantibodies directed against nuclear antigens and immune complex deposition in various tissues leading to target organ inflammation and damage. Although the etiology of SLE is unknown, it has been observed that patients with SLE have lower levels of circulating TGFβ than healthy individuals. In addition, mice lacking the TGFβ1 gene develop a severe autoimmune disease that has features of both SS and SLE. Polymorphisms in the TGFβ1 gene may alter the mRNA expression levels and influence the plasma protein concentration. Of the known TGFβ 1 polymorphisms, only the C-509T polymorphism in the promoter region has been shown to be significantly associated with the plasma concentrations of TGFβ 1. In this study, we have conducted a blinded study to determine if the -509 TGFβ1 gene polymorphism is associated with SS or SLE. Genomic PCR and RFLP analysis of a 441 bp sequence encompassing the –509 polymorphism of the TGFβ gene indicated that there were no statistically significant clinical correlations.