Thiazolidinediones (TZDs) have beneficial effects on markers of cardiovascular risk in patients with type 2 diabetes mellitus (DM). This study aimed to investigate the efficacy and safety of low-dose pioglitazone (15 mg per day) in patients with acute myocardial infarction (AMI) and type 2 DM or impaired glucose tolerance (IGT) treated with coronary angioplasty using bare metal stent (BMS). In 56 patients, pioglitazone was orally administered for 6 months after stenting (pioglitazone group). The incidence of in-stent restenosis (ISR) and left ventricular end-diastolic volume index (LVEDVI) at acute phase and 6 months after stenting in these patients were retrospectively compared with those in the other 37 patients (control group) treated without pioglitazone. No adverse events including death, emergency bypass surgery, and reinfarction, occurred in any patients in the hospital. There was no congestive heart failure (CHF) during a follow-up period in the pioglitazone group. At 6 months after stenting, the overall angiographic ISR rate was significantly lower in the pioglitazone group than in the control group (28.6% vs 48.6%, P = 0.049). In patients with hemoglobin A1c (HbA1c) <7.0% at follow-up, the ISR rate was also significantly lower in the pioglitazone group than in controls (21.3% vs 44.8%, P = 0.03). Delta-LVEDVI (defined as follow-up LVEDVI minus acute LVEDVI) was similar between the pioglitazone group and control group (0.13 vs 5.16 ml/m(2), P = 0.482). Low-dose pioglitazone seems to have a potential to reduce ISR and does not adversely affect LV remodeling after AMI treated with coronary angioplasty using BMS in patients with type 2 DM or IGT.