Our aim was to evaluate the mortality rate and occurrence of complications in patients aged <75 versus ≥75 years with ST-elevation myocardial infarction (STEMI). We studied 1,657 consecutive patients with STEMI hospitalized in the cardiac intensive care unit during 2008 to 2014. All patients underwent primary percutaneous intervention, of which 292 (18%) were aged ≥75 years. Patient records were evaluated for in-hospital complications, 30-day mortality, and long-term mortality over a mean period of 3.4 ± 2.1 years. Compared with younger patients, patients aged ≥75 years had a significantly higher rate of coronary disease risk factors, prolonged symptom duration (512 ± 640 vs 333 ± 545 minutes, p <0.01) and door-to-balloon time (51.1 ± 24 vs 45.6 ± 38, p = 0.02). Patients aged ≥75 years had more in-hospital noncardiac and cardiac complications, including cardiogenic shock and arrhythmia, and had higher 30-day and long-term mortalities. Cardiogenic shock was associated with increased short- and long-term mortality in the older group but was not incremental over the noncardiogenic shock cohort. In conclusion, in patients aged ≥75 years who underwent primary percutaneous intervention for STEMI, the short- and long-term mortality rate was greater than fourfold higher compared with younger patients.