Complete Freund's adjuvant (CFA) is a mixture of dessicated mycobacterium in mannide monooleate and paraffin oil that causes tissue death, lesions, and inflammation. Immunologists have been inducing inflammatory conditions and autoimmune diseases in laboratory animals using CFA for more than 50 years. Rheumatoid arthritis (RA) is a disease marked by ongoing inflammation that affects more than just joints. Twenty male rats were divided into 2 groups (10 each), Normal control group:Rats were not given any medication.. CFA-induced arthritis group: Rats injected with Complete Freund's adjuvant (0.1 ml, once). After 60 days blood sample and Stifle joints were collected for biochemical assay and genetic study of some signaling transducers including IFNγ, Interleukin-4, STAT3 and Interleukin-12. The results revealed that CFA induced RA in rats causing increasing in serum liver enzymes and serum concentration of creatinine,urea,FBS ,RF, Anti-CCP and CRP while decreasing in serum Total antioxidant capacity (TAC) concentration .Moreover up regulation of IL-12, IFNγ and STAT3 gene and down regulation of IL-4 gene in CFA-induced arthritis group contrasted with the control group.