Background: In patients with ST-segment elevation myocardial infarction (STEMI), delay between contact with the health care system and initiation of reperfusion therapy (system delay) is associated with mortality, but data on the associated risk for congestive heart failure (CHF) among survivors are limited. Objective: To evaluate the association between system delay and the risk for readmissions or outpatient contacts due to CHF after primary percutaneous coronary intervention (PPCI) in patients with STEMI. Design: Historical follow-up study using population-based medical registries. Setting: Western Denmark. Patients: Patients with STEMI who were transported by emergency medical service from 1 January 1999 to 7 February 2010 and treated with PPCI within 12 hours of symptom onset and who had a system delay of 6 hours or less (n = 7952). The median duration of follow-up was 3.1 years. Measurements: Cumulative incidence of readmissions or outpatient contacts due to CHF was determined by using competing-risk regression analysis, with death as the competing risk. Crude and adjusted cause-specific hazard ratios for readmissions or outpatient contacts due to CHF were determined for system delay and other covariates. Results: System delays of 60 minutes or less (n = 451), 61 to 120 minutes (n = 3457), 121 to 180 minutes (n = 2655), and 181 to 360 minutes (n = 1389) corresponded with long-term risks for readmissions or outpatient contacts due to CHF of 10.1%, 10.6%, 12.3%, and 14.1%, respectively (P