Background: Follow-up of patients with inferior STEMI having acute significant mitral regurgitation to assess the effect of mitral regurgitation and the type of reperfusion therapy whether thrombolytic therapy or PCI on the prognosis of these patients Patients and methods: This is a prospective, observational, non-controlled study included two hundred and forty patients with inferior STEMI admitted at National Heart Institute from august 2016 to August 2018. The patients were classified into 2 groups according to presence or absence of mitral regurgitation, 120 patients in each group. Group A (ischemic MR) was further subdivided into 2 subgroups, 60 patients who underwent primary PCI and 60 patients who received thrombolytic therapy. Results: Patients presenting with inferior STEMI and having ischemic mitral regurgitation (IMR) had more, in hospital, complications regarding life threatening arrhythmias, cardiogenic shock and mortality. On three months follow-up these patients had more incidence of developing congestive heart failure and low ejection fraction. On analyzing the data of each subgroup, the patients who had IMR and received thrombolytic therapy had more sever mitral regurgitation, more in-hospital complications and more incidence of congestive heart failure than those patients who had IMR but underwent primary PCI. Conclusion: Patients with inferior STEMI and having IMR are at more risk for developing in hospital complications and have higher incidence to develop congestive heart failure. However, in these patients those who underwent primary PCI have much better prognosis than those who received thrombolytic therapy.