Background: Revascularization within a 90-min door-to-balloon time is a strict policy enacted in Taiwan. Prompt diagnosis is critical to avoid an unnecessary procedure and catheterization laboratory activation. This study was aimed to investigate the clinical and prognostic characteristics of the patients with ST-elevation myocardial infarction (STEMI) referred for primary percutaneous coronary intervention (PCI) and normal coronary arteries found following coronary angiography (CAG). Materials and Methods: From October 2009 to December 2012, 216 consecutive patients with STEMI referred for primary PCI were enrolled. The data of clinical history, physical examination, laboratory results, electrocardiography, echocardiography, CAG findings, diagnosis, and outcomes were collected and analyzed. Results: A total of 17 patients were proved normal coronaries angiographically. The incidence of the conditions mimicking as STEMI is 7.9%. Alternative diagnosis was coronary spasm (n = 7), peri-myocarditis (n = 6), apical ballooning syndrome (n = 3), anaphylactic shock (n = 1). Compared with STEMI group, patients in normal coronaries group were younger, with a less premature family history of coronary artery disease (CAD), and reported angina. The 30-day mortality rate in the normal coronaries group was 5.9%. Conclusions: Cautiously evaluating CAD risk factors and symptoms of angina and awareness of alternative diagnosis are important to make a prompt diagnosis without compromising accuracy in the patients presenting as suspected STEMI.