Although primary Sjögren's syndrome is a common rheumatic disorder in women, it is not well recognized in men. This study represents the first report of the clinical, serologic, and immunogenetic features of a group of 36 men with primary Sjögren's syndrome, which are contrasted with those of a group of 69 women with primary Sjögren's syndrome. The majority of male patients had extraglandular involvement including articular (78 percent), neurologic (39 percent), inflammatory vascular (25 percent), and lymphoproliferative disorders (17 percent). Although men were at the same risk for the development of extraglandular complications, there were significant serologic and immunogenetic differences. In sharp contrast to women with Sjögren's syndrome, men with Sjögren's syndrome were seronegative with respect to the presence of serum rheumatoid factor (p = 0.008) and antibodies to Ro(SS-A) (p = 0.016). The supertypic specificity, MT2 (DRw52), as in women, was strongly associated with primary Sjögren's syndrome in men when compared with race-matched control subjects (p = 0.0015). In men, however, the frequency of HLA-B8 and HLA-DR3, the most common DR locus specificity observed in women, was not statistically different from that observed in the normal control group.