Objectives: The impact of periprocedural (before primary percutaneous coronary angioplasty, PCI) abciximab administration on microvascular obstruction in patients with occluded infarct-related artery (IRA) is unknown. Methods: We studied 36 consecutive patients with first ST elevation myocardial infarction (STEMI) and occluded IRA treated with successful primary PCI within 12 h from symptom onset, who received intravenous abciximab immediately before PCI and 49 matched patients who did not receive abciximab as controls. All patients underwent delayed-enhanced magnetic resonance (DE-MR) 6 ± 2 days after PCI. Necrosis was judged as transmural when DE was extended to ≧75% of left ventricular (LV) segment thickness. Severe microvascular obstruction was identified as areas of late hypoenhancement surrounded by DE. Results: Time to treatment was comparable in the two groups (182 ± 60 vs. 188 ± 110 min, respectively). Transmurality and severe microvascular obstruction were present in 3.03 ± 2.8 versus 3.09 ± 2.9 (p = 0.9) and 1.05 ± 1.5 versus 1.06 ± 1.8 (p = 0.6) of LV segments, respectively, in the abciximab group versus controls. At multivariate analysis, severe microvascular obstruction was independently associated only with transmural necrosis (OR 1.5, p < 0.001) and age (OR 1.1, p = 0.02) but not with the use of abciximab. Conclusions: Severe microvascular obstruction after primary PCI of STEMI patients with occluded IRA is related to transmural necrosis but not to the use of abciximab.