The present study was designed in order to determine whether Lonicerae flos (LF) could mitigate rheumatoid arthritis through inhibition of cyclooxygenase (COX)-2 and matrix metalloproteinase (MMP)-9 by regulation of macrophage migration inhibitory factor (MIF). We found that MIF mRNA expression in synoviocytes stimulated with phorbol-12-myristate-13-acetate dose-dependantly decreased by LF extract treatment (0.4 - 1.0 mg/$m{ell}$). The distribution of MIF, COX-2 and MMP-9 positive reacted cells in LPS induced arthritis of mice were decreased by LF (45 mg/kg/day) treatment for 28 days. These data likely indicate that LF may act as MIF inhibitor and may be possible to develop useful agent for rheumatoid arthritis.