We conducted the current study to characterize the clinical presentation of primary Sjögren syndrome (SS) in a large cohort of Spanish patients and to determine whether epidemiologic, clinical, and analytical features modulate disease expression. Patients were from the GEMESS Study group, which was formed in 2005 and included 12 Spanish reference centers. By March 2007, the database included 1010 consecutive patients, recruited since 1994, both incident and prevalent cases. The cohort included 937 women and 73 men (ratio, 13:1), with a mean age of 53 years at diagnosis and 59 years at inclusion in the registry. Multivariate analysis showed that male patients had a lower frequency of thyroiditis, Raynaud phenomenon, and antinuclear antibodies. Young-onset patients had a low degree of sicca involvement (xerostomia and parotid enlargement) and a high frequency of immunologic markers (anti-Ro/SS-A and low C4 levels). Patients with disease duration of more than 10 years had a higher prevalence of xerophthalmia, parotid enlargement, lung involvement, and peripheral neuropathy in comparison with incident cases. The subset of patients with anti-Ro/La antibodies had the highest prevalence of most systemic, hematologic, and immunologic alterations (higher frequency of Raynaud phenomenon, altered parotid scintigraphy, positive salivary gland biopsy, peripheral neuropathy, thrombocytopenia, and rheumatoid factor). Hypocomplementemia was associated with a higher frequency of vasculitis and lymphoma, and cryoglobulins with a higher frequency of parotid enlargement, vasculitis, and leukopenia.Epidemiologic, clinical, and analytical features have a significant impact on the clinical presentation of primary SS, influencing the results of the main diagnostic tests, the prevalence and diversity of extraglandular involvement, and the frequency of the main immunologic markers. Primary SS should be considered as a systemic autoimmune disease that can express in many guises beyond sicca involvement.