The present prospective non-randomized study aimed to examine whether intraaortic balloon counter-pulsation (IABP) has a favorable effect on QT dispersion in patients with acute anterior MI. Patients with acute anterior MI who presented within 6 h after the symptom onset were assigned to the IABP + streptokinase or streptokinase (STK) group. The IABP + STK group was consisted of 26 men and two women (mean age 52.9+/-10.2). The STK group was consisted of 19 men and two women (mean age 54.4+/-10.8). In the IABP + STK group, mean QT interval dispersion significantly shortened 6 h after treatment (50.9+/-15.6 ms before STK, and 36+/-13.9 ms 6 h after STK; P = 0.001) and did not significantly change 24 h after STK (35.6+/-11.2 ms). In the STK group, mean QT interval dispersion did not vary significantly before and 6 h after STK (57.14+/-13.2 ms before STK, and 56.07+/-13.3 ms 6 h after STK; P > 0.05) but 24 h after STK it significantly shortened to 40.42+/-10.8 ms (P < 0.001). Before STK, mean QT interval dispersions in the IABP + STK and STK groups were 50.9+/-15.6 ms and 57.14+/-13.2 ms, respectively (P > 0.05), 6 h after STK, mean QT interval dispersions were 36+/-13.9 ms and 56.07+/-13.3 ms, respectively (P = 0.0001) and 24 h after STK, mean QT interval dispersions were 35.6+/-11.2 ms and 40.42+/-10.8 ms, respectively (P > 0.05). In conclusion this study demonstrates that the adjunct of IABP to thrombolytic therapy, in the setting of acute anterior MI, significantly decreases QT interval dispersion at 6 h and this effect might be secondary to accelerated reperfusion and/or other beneficial effects of IABP.