Adiponectin (Acrp30, AdipoQ, GBP28) is a biologically active protein built from 244 amino acids of about 28kDa molecular mass. It is coded in humans through the ACDC gene (APM1), whose transcripts quantitatively predominate in adipocytes. The PPAR gamma receptor may play the main part in the adjustment of ACDC gene expression. There are two domains in protein building adiponectin: the first is globular, placed on the carboxyl end, and this sequence demonstrates large similarity to the sequence of the complement protein C1q; and the second is fibrous, on the amine end, this structure resembling collagen types VIII and X. We can distinguish three main adiponectin fractions (LMW, MMW, HMW) in human serum which differ among themselves in molecular mass. They represent the adiponectin at different degrees of oligomerization. Adiponectin prevents obesity and vessel diseases, but one can suggest in joints its inflammatory influence. In RA patients there were significantly higher concentrations of adiponectin in sera in comparison with the control group and higher levels of adiponectin in synovial membrane in joints in RA patients than in joints of patients with osteoarthritis.