Background:Inter-facility transfer for primary percutaneous coronary intervention (PCI) from referring facilities to PCI centers causes a significant delay in treatment of ST-segment elevation acute myocardial infarction (STEMI) patients undergoing primary PCI. However, little is known about the clinical outcomes of STEMI patients undergoing inter-facility transfer in Japan.Methods and Results:In the CREDO-Kyoto acute myocardial infarction (AMI) registry that enrolled 5,429 consecutive AMI patients in 26 centers in Japan, the current study population consisted of 3,820 STEMI patients who underwent primary PCI within 24 h of symptom onset. We compared long-term clinical outcomes between inter-facility transfer patients and those directly admitted to PCI centers. The primary outcome measure was a composite of all-cause death or heart failure (HF) hospitalization. There were 1,725 (45.2%) inter-facility transfer patients, and 2,095 patients (54.8%) with direct admission to PCI centers. The cumulative 5-year incidence of death/HF hospitalization was significantly higher in the inter-facility transfer patients than in those with direct admission (26.9% vs. 22.2%; log-rank P<0.001). After adjusting for potential confounders, the risk for death/HF hospitalization was significantly higher (adjusted hazard ratio: 1.22, 95% confidence interval: 1.07–1.40, P<0.001) in the inter-facility transfer patients than in those directly admitted.Conclusions:Inter-facility transfer was associated with significantly worse long-term clinical outcomes for patients with STEMI undergoing primary PCI.