OBJECTIVE:We compared 1-year outcomes in insulin-treated diabetes mellitus (ITDM) and non-ITDM patients compared to nondiabetic (DM) patients following contemporary percutaneous coronary intervention (PCI). BACKGROUND:ITDM is associated with extensive atherosclerotic disease and worse cardiovascular prognosis compared to non-ITDM patients. METHODS:We evaluated PCI patients at a large tertiary center from 2010 to 2016, grouped according to diabetes and treatment status at baseline. One-year major adverse cardiac events (MACE) were defined as a composite of death, myocardial infarction (MI), or target vessel revascularization. Outcomes were adjusted using multivariable Cox regression methods. RESULTS:During the study period, 16,889 patients underwent PCI including 13.7% ITDM, 34.0% non-ITDM, and 52.3% non-DM patients. Patients with DM were younger, including more females and non-white patients, with higher body mass index and greater prevalence of prior revascularization and chronic kidney disease. Compared to others, ITDM patients more often presented with acute coronary syndrome, in-stent restenosis, or severe lesion calcification. There were no differences in discharge rates of dual antiplatelet therapy and statins, whereas beta-blockers were more commonly prescribed in DM patients. At 1-year, both ITDM and non-ITDM patients had greater risk of MACE compared with non-DM patients, and ITDM conferred greater adjusted risk than non-ITDM (ITDM = HR: 2.11, 95% CI [1.79,2.50]; non-ITDM = HR: 1.27, 95%CI [1.09,1.47]). CONCLUSIONS:The negative prognostic effect of DM following contemporary PCI is heightened in the presence of insulin treatment, compared to non-DM patients. Focus on secondary prevention, prescription of and adherence to optimal medical therapy is necessary for post-PCI risk reduction.