We have studied the influences of age on clinical manifestations and serological abnormalities in primary Sjögren's syndrome (pSS). The 67 patients included were diagnosed according to the preliminary European classification criteria for pSS, and disease manifestations were assessed according to a newly developed quantitative and qualitative classification model. We found that the age at diagnosis correlated to the presence of autoantibodies anti-SSA/SSB (r=-0.31, <0.02), rheumatoid factor (RF) (r=-0.33, p<0.01) and serum levels of IgG (r=-0.27, p<0.05). Young patients diagnosed before 45 years of age had the highest positivity of the autoantibodies anti-SSA/SSB (62.5%), RF (62.5%) and high levels of s-IgG (68.8%), while the corresponding values for old patients diagnosed after 60 years of age were anti-SSA/SSB: 20.8%, RF: 20.8%, and high s-IgG: 29.2%. None of these parameters correlated to age at onset nor disease duration. By applying a model for evaluating disease manifestations, no correlation between the global index nor the indices for subgroups of disease manifestations was found to age at onset, age at diagnosis, nor disease duration. We conclude that there is a significant influence of age on serological abnormalities in pSS, but not on disease manifestations.