The clinical course of 48 patients with primary Sjögren's syndrome (primary SS) was reviewed. Forty-three north European patients were typed for HLA class I and class II alloantigens. In this population with primary SS HLA B8, DR3 and DRw52 all occurred more frequently than in the control population (P < 0.009, P < 0.0035, P < 0.02 respectively). The subgroup of primary SS patients with antibodies to Ro and/or La antigen had the greatest prevalence of DR3 (relative risk 33.4). The primary SS patients fall into two distinct groups: those with extraglandular disease in whom lymphopaenia, hypergammaglobulinaemia, antibodies to Ro and/or La and HLA DR3 were all more frequent and those patients with either glandular disease alone or only one extraglandular feature. There was no difference in disease duration between the two groups, although on average the latter group were 10 years older.