Background: Rapid door-to-needle time with thrombolytic therapy is associated with lower mortality in patients with acute myocardial infarction (AMI). However, data on time to primary percutaneous coronary angioplasty (PCI) and its relationship to mortality are still controversial. Objectives: The aim of this study was to evaluate the impact of 3 time variables (Symptom onset-to-door time, Door-to-balloon time, and Symptom-onset-to-balloon time) on the clinical outcomes and to define the subgroups that were mostly influenced by the time variables in the AMI patients who underwent primary angioplasty in Korea. Methods: The Korea Acute Myocardial Infarction Registry (KAMIR) is the nationwide study for AMI. We conducted interim analysis of 4517 patients at 41 hospitals who participated in the KAMIR between October 2005 and July 2006. Among 4517 patients, we included 705 ST-elevation myocardial infarction (STEMI) patients who presented within 12 hours of symptom onset and were treated with primary PCI. We evaluated and compared the effect of symptom onset-to-door time, door-to-balloon time, and symptom onset-to-balloon time on 1-month mortality. Results: Mortality at 1-month was 5.7%. The median of symptom onset-to-door time, door-to-balloon time, and symptom onset-to-balloon time was 151 (interquartile range: 85-287), 68 (45-120), and 245 minutes (160-435) respectively. One-month mortality did not increase significantly with increasing delay in symptom onset-to-door time (5.2% and 5.9% for ���120 min and >120 min; p=0.7), door-to-balloon time (5.4% and 6.2% for ���90 min and >90 min; p=0.678), and symptom onset-to-balloon time (5.7% and 5.6% for ���240 min and >240 min; p=0.963). When we performed subgroup analysis according to age, sex, Killip class, and diabetes, 3 time variables were not significantly associated 1-month mortality. Conclusion: This study doesn���t show that, in patients with STEMI treated by primary PCI, symptom-onset-to-door time, door-to-balloon time, and symptom-onset-to-balloon time are related to 1-month mortality. These time variables did not have impact on 1-month mortality in any subgroup. The effects of delay to treatment with primary PCI on mortality warrant further study.