Background Although octogenarians constitute a fast growing portion of cardiovascular patients, few data are available on the outcome of very old patients (age >80 years) with ST-segment elevation myocardial infarction (STEMI) undergoing primary angioplasty. Methods and Results Short- and long-term outcomes of 88 consecutive very old (age ≥85 years) patients with STEMI undergoing primary angioplasty were evaluated. In-hospital mortality was 17%, significantly higher in patients with cardiogenic shock (90%; p<0.001), with failure of percutaneous coronary intervention (PCI; p=0.016), with Killip class ≥III on admission (p=0.018), or with chronic renal failure (p=0.033). Major bleeding complications occurred in 11 patients (12%). Multivariable logistic regression analysis identified 3 independent predictors of in-hospital death: age ≥90 years (p=0.018), Killip ≥III on admission (p=0.018), and PCI failure (p=0.025). Multivariable logistic regression analysis identified age ≥90 years (p=0.008), Killip ≥III on admission (p=0.015), and time from symptoms to PCI >12 h (p=0.04) as independent predictors of mortality at long-term follow-up. Conclusions The low incidence of procedural complications, together with good long term survival, suggest that primary PCI in STEMI patients ≥85 years is safe and efficacious, with a low rate of PCI failure in the presence of a low Killip class on admission, whereas primary PCI is unable to affect the poor prognosis for very old patients with cardiogenic shock. (Circ J 2008; 72: 67 - 70)