The FN promotes macrophage adherence, and is chemotactic for fibroblasts. These proporties sugest a role for FN in the modulation of joint inflammation. Other way it seemed that this protein concerned in the organization and repair of damaged or imflammed articular tissues. 98 synovial fluids speciments were evaluated. 56 postraumatic arthropaties, 26 arthrosis and 16 reumathoid arthritis. The authors have considered as parameters oflaboratory: proteins, G. A and M Immunoglobulins, C3 and C4 and FN. A statiscally significative medium increase appeared between de FN values arthritis reumathod's synovial fluids (583,5 ±2 142,8) when it is compared with postraumatic arthropaties (363,8 ±214,5) p< 0.00. and with osteoarthritis ( 429,1 ±2 80,9) p< 0.01. Artritis reumathoid grup showed also a significantly increase between the values ofFN in Synovial fluids when it is compared with plasmatic levels (399,2 ±2 137,4) p< 0.001. The increases in the levels ofthe FN, have been attributing to a organic necessity of disposing of an unspecific opsonin which facilitate and provide the elimination of inert rests.