This study was performed to investigate the hemodynamic changes which occur after occlusion of coronary artery and relation to reperfusion arrhythmias(RA) which occur when occlusion materials were removed form coronary artery in dogs. The occlusion of coronary artery was designed by temporary ligation of left circumflex branch of coronary artery during 30 minutes in 16 dogs. During occlusion of coronary artery, cardiac output(CO), mean aortic pressure (mAP), aortic systolic pressure(ASP), aortic diastolic pressure(ADP). left ventricular systolic pressure(LVSP), left ventricular maximum dp/dt (LV max. dp/dt) and left ventricular end-diastolic pressure (LVEDP) were measured. The occurrence of RA were observed for 5 minute after reperfusion by explained of ligation. As a results, cardiac arrest occurred in 4 dogs during occlusion of coronary artery, and RA was not observed in 5 dogs while it was seen in 5 dogs when explained ligation(reperfusion) after 30 minutes, the rest 2 dogs occurred temporary tachycardia. In hemodynamics changes, LVSP decreased by 10.9% and LV max. dp/dt by 5.4 % in comparison to control value which not ligated coronary artery, and LVEDP increased by 73.3%. The CO/min and mAP also decreased by 10.7% and by 11.3% expectedly. In the relationship to occurrence RA and hemodynamics changes, the LVSP and LV max. dp/dt at the time of occlusion in the RA group decreased by 11.9% and 0.8% in comarison to the control value while the decrease was 7.7% and 10% in the non-RA group. But the LVEDP in creased by 109.1% in the RA group while the decreased was 44.6% in the non-RA group. Referring CO/min, the drop was 8.8% in the RA occurrence group and 12.9% in the non-occurence group. These parameters of LVEDP, LV max. dp/dt, and CO were significant difference(p<0.05). The mAP also decreased by 11.9 in the RA group and by 9.8% in the non-RA group, but these defference were not the significant difference.