<i>Objective:</i> To examine whether the outcomes of diabetic patients after successful percutaneous coronary revascularization are influenced by the modality of treatment for hyperglycemia at the time of percutaneous coronary revascularization. <i>Design:</i> Retrospective analysis of the Mayo Clinic PTCA Registry. <i>Material and Methods:</i> We examined whether the modality of treatment of diabetes mellitus (diet alone vs. oral hypoglycemics vs. insulin) impacted on the occurrence of death and death/myocardial infarction among diabetic patients after successful percutaneous coronary revascularization from January 1, 1995 through December 1998. <i>Results:</i> Of the 821 diabetic patients with known treatment status, 129 received diet alone, 370 oral agents, and 322 insulin. The clinical success rates of percutaneous coronary revascularization were similarly high among the groups (>90%). The adjusted risk of suffering either death or death/myocardial infarction after successful percutaneous coronary revascularization was greater for insulin-treated patients (vs. non-insulin): relative risk (95% confidence intervals) of 1.65 (0.99, 2.72) and 1.65 (1.20, 2.27), respectively. Patients treated with oral agents had lower risk of suffering death or death/myocardial infarction than insulin-treated patients (0.59 [0.36, 0.99] and 0.57 [0.38, 0.84], respectively), with a similar trend for patients on diet alone (0.96 [0.48, 1.99] and 0.65 [0.36, 1.16], respectively). <i>Conclusions:</i> Although the clinical success rates of PCR were similar for insulin- and non-insulin-treated diabetic patients, insulin-treated patients had worse long-term outcomes after successful percutaneous coronary revascularization.