Background: Primary angioplasty is the most effective treatment of ST-segment elevation acute myocardial infarction (STEMI). However, its worldwide implementation is difficult to obtain. Therefore thrombolysis continues to be the treatment most commonly used. Aim: To evaluate in-hospital and long term mortality of patients with STEMI treated with thrombolysis or angioplasty, in three hospitals participating in the Chilean National Registry of Acute MI (GEMI group). Material and methods: Registry of 1,634 consecutive patients with STEMI admited between 2002 and 2006. Risk was stratified using the Thrombolysis in Myocardial Infarction(TIMI) Risk Score. Hospital and log term mortalities were adjusted using logistic and Cox regression models. Results: Fifty nine percent of patients (967 patients aged 60 +/- 12 years, 77% males) were subjected to reperfusion therapies, 28% with primary angioplasty and 72% with thrombolysis. Hospital mortality rates among patients treated with thrombolysis and angioplasty were 10.9% and 5.6% (p=0.01), respectively. The figures for long term mortality were 20.4% and 9.7%, respectively (p < 0.01). Multivariate analysis confirmed the lower mortality among subjects treated with angioplasty with an odds ratio (OR) in favour of angioplasty of 8.5 (95% confidence intervals (CI) 3-35) for in hospital mortality and of 4.7(95% CI 2.6-8.3) for long term mortality. The higher benefits of angioplasty were observed in males, in the elderly and in patients with a TIMI score over > 3. Conclusions: Hospital and long term mortality of patients with STEMI was lower among those treated with primary angioplasty. This treatment is most beneficial among males, in the elderly and in patients with a TIMI score > 3 (Rev Med Chile 2008; 136: 1098-106).