The serological profiles of 54 patients with primary Sjögren's syndrome (pSS) and 92 rheumatoid arthritis (RA) patients with or without secondary SS (sSS), were retrospectively evaluated and correlated with: different subgroups of SS, degree of minor salivary gland biopsy lymphocytic infiltrates and the presence of glandular and extraglandular manifestations. Antibodies to nuclear antigens (ANA), anti-Ro(SSA) and anti-La(SSB) as well as rheumatoid factor (RF) correlate with definite pSS, while in RA, ANA and anti-Ro(SSA) are associated with the presence of sSS and anti-La(SSB) is practically absent. In pSS patients, the incidence of anti-Ro(SSA) and anti-La(SSB), as well as the titers of ANA and RF, correlate with the degree of salivary lymphocytic infiltrates in class 1+ to 3+. In class 4+, a substantial decrease of the autoantibodies is noted. In pSS patients, anti-Ro(SSA) and anti-La(SSB) correlate with earlier disease onset and longer disease duration, recurrent parotid gland enlargement (RPGE), as well as with the presence of extraglandular manifestations (extr. manif.) particularly splenomegaly/lymphadenopathy and vasculitis. Anti-Ro(SSA) correlates with positive Schirmer's test, ANA with decreased parotid flow rate and extr. manif., while RF correlates with RPGE and subjective xerostomia. In RA patients, autoantibodies were predominantly found in the presence of features of eye dryness: ANA correlate with positive Schirmer's test, Rose-Bengal stain and subjective xerophthalmia, the latter also correlated with anti-Ro(SSA). This study, re-emphasizes the diagnostic significance of autoantibodies for SS, and possibly contributes in the delineation of biological processes in this disease.