Japanese patients with primary Sjögren's syndrome (SS), patients with SS and rheumatoid arthritis (SS-RA), and patients with SS and connective tissue disease without RA (nonrheumatoid connective tissue disease [SS-CTD]) were typed for HLA antigens. Patients with primary SS and those with SS-RA had higher frequencies of DRw53 than did those who had SS-CTD; however, the group with SS-CTD showed a negative correlation with DRw52. These data indicate that Japanese and white patients with SS have different HLA specificities, and that genetic factors involved in the development of SS-CTD might be different from those in primary SS and SS-RA.