Background and Objectives: The no-reflow phenomenon after primary percutaneous coronary intervention (PCI) is associated with greater infarct size, worse functional recovery, and higher incidence of complication after acute ST-elevation myocardial infarction (STEMI). The aim of this study was to assess the relation between preprocedural N-terminal pro-B-type natriuretic peptide (NT-proBNP) and angiographic no-reflow phenomenon. Methods: We measured preprocedural serum NT-proBNP level in 174 consecutive acute STEMI patients (63.7짹11.7 years, male 70 %) on admission and before PCI. Angiographic no-reflow after PCI was defined as Thrombolysis in Myocardial Infarction (TIMI) flow grade <3. Results: The baseline characteristics including measuring time from the chest pain onset between the groups with no-relow group (n=73) and normal reflow group (n=96) are similar. The level of NT-proBNP was significantly higher in the no-relflow group than that in the normal reflow group (2628.2짹4953.3 vs. 510.5짹874.6 pg/mL, p=0.001). Also, the level of high sensitivity C-reative protein (hs-CRP), monocyte, and troponin-T were significantly higher in the no-reflow group than those in the normal reflow group. There were no significant differences in the distribution of target vessel or number of receiving intravenous or intraconary abciximab administration between the groups. In no-reflow group, NT-proBNP level was much higher in patients with TIMI flow grade 0 (n=48, 3063.5짹5917.5 pg/mL) than that in patients with TIMI grade I or II (n=25, 1814.3짹2139.4 pg/mL). The area under the receiver-operating characteristic (ROC) curve for NT-proBNP level was 0.77, and the optimal cut-off value identified by ROC analysis was 500 pg/mL. At the standard cutpoint of > 500 pg/mL, elevated NT-proBNP level showed high probability of no-reflow phenomenon (odd ratio, 5.84; 95% CI, 2.43 to 14.06; p<0.001). In multivariate analysis, the NT-proBNP was an independent predictor for no-reflow phenomenon along with troponin-T, whereas hs-CRP and monocyte were not. Conclusion: Preprocedural NT-proBNP is a strong predictor for the development of no-reflow phenomenon after PCI in patients with acute STEMI.