The goal of this study was to evaluate the role of Doppler time interval-derived myocardial performance index (MPI) in the setting of acute right ventricular myocardial infarction (RVMI). Inferior myocardial infarction is accompanied by RVMI in over a third of cases. We do not have easily applicable noninvasive tools for reliably quantifying the right ventricular (RV) dysfunction in RVMI and to serially follow alterations. Clinical and echocardiography data of all acute inferior myocardial infarction (IMI) admissions (n = 135) to our referral teaching institute were prospectively collected for the study. After exclusions, study group comprised of 36 patients with RVMI diagnosed by ≥1 mm ST segment elevation in V3R-V5R of right-sided ECG and 63 patients without RVMI constituted the control group. All patients underwent echocardiography within 24 hours of admission. Normal range of MPI for our laboratory was estimated from 50 age-matched healthy subjects. RV MPI was elevated to a mean of 0.53 ± 0.22 in RVMI (Normal MPI 0.20 ± 0.05, P-value < 0.001). IMI without RVMI did not elevate MPI significantly (0.21 ± 0.17, P-value NS). Repeat MPI estimation in 11 RVMI (7 thrombolyzed) patients after 5 days showed dramatic reduction (0.23 ± 0.12, P-value < 0.001). This reduction was noted irrespective of thrombolysis. RV MPI ≥ 0.30 has high sensitivity (82%) and specificity (95%) for the diagnosis of RVMI in the presence of acute IMI. MPI can reliably diagnose RV infarction. It can be used to quantify right ventricular dysfunction and assess acute improvements in RV function.