We report 6 patients with an established diagnosis of primary Sjögren syndrome who developed severe rheumatoid arthritis (RA) requiring oral disease-modifying antirheumatic drug with or without biologic therapy. Rheumatoid arthritis was diagnosed between 14 months and 17 years following initial sicca symptoms. Five patients were female. Two thirds were seropositive for Sjögren antibody, and 5 of 6 were either rheumatoid factor or anti-cyclic citrullinated peptide positive at the time of RA diagnosis. All had either hand or wrist involvement; one third had nodules. Although none demonstrated erosion on x-ray, all required methotrexate or leflunomide, and 4 required a biologic agent for the treatment of their arthritis. Primary Sjögren patients may develop RA after a long course of stable Sjögren.