Solanum Iyratum Thunb (Solanaceae) has multiple applications in korean traditional medicine because of its cytotoxic, immunological and anti-inflammatory activities. However, no study on the anti-arthritic activity of Solanum Iyratum Thunb has been reported in vivo. Rheumatoid arthritis (RA) is a systemic autoimmune disease with chronic inflammation characterized by hyperplasia of synovial cells in affected joints, which ultimately leads to the destruction of cartilage and bone. Cytokine production were assessed during CIA(collagen-induced arthritis) model mice in lymph node (LN), in knee joint and spleen, using ELISA. DBA/1j mice were immunized with bovine type II collagen. After a second collagen immunization, mice were treated with Solanum Iyratum Thunb (SLT) orally at 400, 200 mg/kg once a day for 4 weeks. The severity of arthritis within the knee joints was evaluated by histological assessment of cartilage destruction and pannus formation. SLT significantly suppressed the progression of CIA and inhibited the production of TNF-alpha and IFN-gamma in serum and spleen cell culture supernatant. The erosion of cartilage was dramatically reduced in mouse knees after treatment with SLT. In conclusion, our results demonstrates that SLT significantly suppressed the progression of CIA. This action was characterized by suppression of arthritis index, cartilage erosion and synovial cell infiltration and the decreased production of $TNF-{alpha}$, $IFN-{gamma}$, CD4+, CD19+, CD3+/CD69+ cells (in lymph node), CD11b+/Gr-1 + (in knee joint).