The objective of the study is to compare the longitudinal performance of different classification criteria for primary Sjögren's syndrome (SS) in a cohort of patients previously diagnosed with primary SS. In each patient, we repeated diagnostic tests as required by the Copenhagen, European, Californian, and American-European Consensus Group (AECG) or the new American College of Rheumatology (ACR) classification criteria. Sixty-three out of 90 eligible patients (70 %) consented to participate. During the follow-up (mean (standard deviation, SD) 7.6 years (0.5)), we observed evolution from primary SS to SS with another systemic autoimmune disease (SAD) in 9/63 (14 %) patients, on average after 4.0 years (SD 0.9). The evolution from primary SS to SS-SADs was significantly more common if the diagnosis of primary SS was initially made using AECG (17 %, p = 0.008) or ACR (16 %, p = 0.016) criteria. In the 34 patients who underwent a full diagnostic reassessment, the diagnosis retention rate was statistically significant for all the criteria, except the European criteria. At reassessment, 3/32 (9 %) patients initially diagnosed as having primary SS using the European criteria could not be classified as having primary SS by any of the criteria. The differences in classification when using the AECG and the new ACR criteria were not statistically significant. The longitudinal diagnosis retention rate was highest for the Californian and AECG criteria. Regardless of the classification criteria, some patients eventually develop another SAD.