The aim of this study was to investigate the possible relationship between the degree of inflammatory infiltration of salivary glands in Sjögren's syndrome (SS) and the different demographic, clinical and serological features of the disease. A quantitative assessment of the extension of the infiltrates was performed on histology samples from the labial salivary glands (LSG) of 82 patients with primary SS, by calculating the ratio of the infiltrated area to the total area of glandular tissue in the samples. The correlations between the amount of inflammatory infiltrate and the main features of the disorder were then analysed. A significant negative correlation between the degree of LSG infiltration and the patient's age at disease onset was observed (P < 0.05). In contrast, the percentage of infiltrate did not correlate with the disease duration. A significant correlation was found between the degree of infiltration of the salivary tissue and (i) the total number of extraglandular features (P < 0.01) and (ii) the presence of specific extraglandular features such as Raynaud's phenomenon (P < 0.05), vasculitis (P < 0.0001), lymph node or spleen enlargement (P < 0.05) and leucopenia (P < 0.02). Finally, patients with antinuclear antibodies, anti-SSA/Ro antibodies, or anti-SSA/Ro plus anti-SSB/La antibodies showed a more widespread inflammatory infiltration in the LSG tissue than patients without these autoantibodies (P < 0.01). The degree of infiltration in the salivary tissue was significantly greater in those patients with anti-SSA/Ro plus anti-SSB/La antibodies in their sera than in patients with anti-SSA/Ro antibodies alone (P < 0.05). In conclusion, patients with SS and active inflammatory infiltration of the salivary glands usually experience an earlier disease onset and a larger number of systemic extraglandular manifestations. In addition, the antibodies directed against certain nuclear/cytoplasmic specificities, and particularly those which react with the SSB/La antigen, seem to play a key role in enhancing the autoimmune process in the salivary glands.