Background: Today, cardiologists seek to minimize time from symptom onset to interventional treatment for the most favorable results. Hypothesis: In the acute coronary syndrome (ACS) symptom complex, sweating can differentiate ST-segment elevation myocardial infarction (STEMI) from non-ST-segment elevation ACS (NSTE-ACS) during early hours of infarction. Methods: This single-center, prospective, observational study compared symptoms of STEMI and NSTE-ACS patients admitted from August 2012 to July 2014. Results: Of 12 913 patients, 90.56% met ACS criteria. Among these, 22.51% had STEMI. Typical angina was the most common symptom (83.82%). On stepwise multiple regression, sweating (odds ratio: 97.06, 95% confidence interval [CI]: 82.16-114.14, P < 0.0001) and typical angina (odds ratio: 2.72, 95% CI: 2.18-3.38, P < 0.001) had significant association with STEMI. For diagnosis of STEMI, positive likelihood ratio (LR) and positive predictive value (PPV) were highest for typical angina with sweating (LR: 11.17, 95% CI: 10.31-12.1; PPV: 76.09, 95% CI: 74.37-77.75), followed by sweating with atypical angina (LR: 3.6, 95% CI: 3.07-4.21; PPV: 50.61, 95% CI: 46.45-54.76), typical angina (LR: 1.05, 95% CI: 1.03-1.07; PPV: 22.97, 95% CI: 22.11-23.84), and atypical angina (LR: 0.77, 95% CI: 0. PPV: 18.09,). C statistic values of 0.859 for typical angina with sweating and 0.519 for typical angina alone reflected high discriminatory value of sweating for STEMI prediction. Conclusions: Presence of sweating with ACS symptoms predicts probability of STEMI, even before clinical confirmation. Sweating in association with typical or atypical angina is a much better predictor of STEMI than NSTE-ACS.