Macrophage　migration　inhibitory　factor　(MIF)　has　been　reported　as　an　inflammatory　cytokine　in　many　inflammatory　diseases,　including　rheumatoid　arthritis　and　ischemic　diseases.　However,　dynamic　changes　of　MIF　within　the　first　24　hours　on　admission　and　potential　prognostic　significance　following　ST-elevation　myocardial　infarction　(STEMI)　have　been　little　known.　In　this　study,　we　examined　the　dynamic　change　of　MIF　level　and　its　potential　diagnostic　and　prognostic　value　after　the　onset　of　STEMI.　Plasma　MIF　levels　were　evaluated　in　symptomatic　subjects　who　received　coronary　angiogram　with　a　median　27　months　follow-up　for　the　development　of　major　adverse　cardiovascular　events　(MACEs).Of　all　993　subjects,　patients　with　STEMI　showed　a　significantly　higher　MIF　levels　than　in　patients　with　non-ST　elevation　acute　coronary　syndrome,　stable　angina,　and　normal　coronary　artery,　respectively　(P　＜　.01).　Plasma　MIF　levels　elevated　as　early　as　12　hours　post-onset　of　STEMI　and　peaked　rapidly　within　24　hours,　and　remained　elevated　from　about　day　5　till　day　9　during　hospitalization.　In　multivariate　analysis,　MIF　was　associated　with　a　decreased　risk　of　MACEs　occurrence　in　STEMI　patients　after　adjustment　for　traditional　cardiovascular　risk　factors　[hazard　ratio　0.81,　(0.72-0.90),　P　＜　.001].　The　ROC　curve　for　MACEs　was　0.72　(95%　CI　0.62-0.80,　P　＜　.001)　and　0.85　(95%　CI　0.80-0.90,　P　＜　.001)　using　Framingham　risk　factors　only　and　combined　with　MIF,　individually.Measurement　of　MIF　adds　potential　information　for　the　early　diagnosis　of　acute　STEMI　and　significantly　improves　risk　prediction　of　MACEs　when　added　to　a　prognostic　model　with　traditional　Framingham　risk　factors.