Real time myocardial contrast echocardiography (RTMCE) is a cost-effective and simple method to quantify coronary flow reserve ( CFR). We aimed to determine the value of RTMCE to predict cardiac events after percutaneous coronary intervention ( PCI). We have studied myocardial blood volume (A), velocity ( β), flow indexes ( MBF, A × β), and vasodilator reserve (stress-to-rest ratios) in 36 patients with acute coronary syndrome ( ACS) who underwent PCI. CFR ( MBF at stress/ MBF at rest) was calculated for each patient. Perfusion scores were used for visual interpretation by MCE and correlation with TIMI flow grade. In qualitative RTMCE assessment, post- PCI visual perfusion scores were higher than pre- PCI (Z = −7.26, P < 0.01). Among 271 arteries with TIMI flow grade 3 post- PCI, 72 (36%) did not reach visual perfusion score 1. The β- and A × β-reserve of the abnormal segments supplied by obstructed arteries increased after PCI comparing to pre- PCI values (P < 0.01). Patients with adverse cardiac events had significantly lower β- and lower A × β-reserve than patients without adverse cardiac events. In the former group, the CFR was ≥ 1.5 both pre- and post- PCI. CFR estimation by RTMCE can quantify myocardial perfusion in patients with ACS who underwent PCI. The parameters β-reserve and CFR combined might predict cardiac events on the follow-up.