Background The optimal duration of dual antiplatelet therapy (DAPT) after acute coronary syndrome (ACS) is not known. Factors influencing DAPT duration are not well described. Hypothesis We hypothesized that continued DAPT 12months beyond ACS would be associated with patient factors such as stent type and that it may be associated with lower rates of ischemic events. Methods The TIMI 38 Coronary Stent Registry (CSR) followed patients who completed the TRITON-TIMI 38 trial, received a stent, and were alive and event free. Continuation of DAPT was determined by the treating physician. Results The CSR enrolled 2110 patients (1679>12months from index ACS) and followed for a median of 2.1 additional years. DAPT was continued in 554 (26%) and was more likely to be continued in patients with drug-eluting stents (DES; 54%) and in North America. The rate of cardiovascular death, MI, or stroke was 2.35% per year, and 13 patients (0.6%) experienced Academic Research Consortium definite or probable ST. Recurrent ischemic events were similar between patients who continued thienopyridine therapy and those who stopped at registry entry (P=0.74 for cardiovascular death/MI/stroke; P=0.72 for definite or probable ST). After propensity score adjustment, there was no significant difference in cardiovascular death/MI/stroke (P=0.55) or bleeding (P=0.51) with prolonged DAPT. Conclusions Patients stabilized for a year after ACS and stenting have low rates of ST relative to overall cardiovascular events. The decision to continue DAPT maybe associated with stent type (DES vs bare-metal stent) and region.