An increased level of glycoproteins (seromucoid, protein-bound hexoses, protein-bound hexosamines, protein-bound sialic acids) was found in the blood serum from patients with rheumatoid arthritis (RA) as compared with healthy individuals. Higher glycoprotein content was observed in the seropositive RA patients than in the seronegative ones. Higher levels of glycoproteins was also observed in the synovial fluid from seropositive RA patients than in the seronegative ones.