This study investigated the effects of altitude on occurrence of mid-term negative events among patients presenting with ST elevation myocardial infarction (STEMI). This study enrolled 492 patients with STEMI. 119 of those patients were living at an intermediate altitude (1960 m, Group I) and 373 were living at sea level (0 m, Group II). There was no significant difference between the different altitude groups in terms of the incidence of cardiac death, urgent target vessel revascularization (TVR), stroke/transient ischemic attack (TIA) and composite endpoints. However, Group I had a significantly higher reinfarction incidence when compared with the Group II. Independent predictors of 6-month composite endpoints were history of statin use, presentation with acute stent thrombosis, peak CK-MB level, success of procedure, Killip classification, and left ventricular ejection fraction. In conclusion, altitude status and altitude-related hematologic changes had no influence over the mid-term outcomes in STEMI patients treated with percutaneous intervention.