Thirty-six wistar rats (150-250 g body weight) were randomly divided into two groups. There were equal numbers of male and female rats in each group. Each group of rats was given either 0.5 ml normal saline or calcitonin generelated peptide (CGRP, 20 μg/kg dissolved in 0.5 ml normal saline) intravenously within 5 min. Coronary arteries of these rats were occluded 5 min after administration. The coronary artery was then released from ligation 5 min later. The heart beat of all rats was monitored for 30 min. An electrocardiogram was recorded using limb leads and belowxiphoid leads. There was no ischemic reperfusion-induced arrhythmia in the first minute of reperfusion in CGRP group, while 13 rats occurred ischemic reperfusion-induced arrhythmia (ventricular tachycardia and fibrillation) in the normal saline group (P < 0.05). Average onset time of ischemic reperfusion-induced arrhythmia was 377.5 ± 141.0 s/sim. In the CGRP group, compared with 42.7 ± 55.4 s/sim. for the normal saline group (P < 0.01). The duration of ischemic reperfusion-induced arrhythmia was 15.0 ± 30.6 s/sim. In the CGRP group compared with 104.4 ± 143.8 s/sim. in the normal group (P < 0.05). There was no death in the CGRP group, but six rats in the normal saline group died (P < 0.05). The results showed that CGRP could reduce and delay the occurrence of ischemic reperfusion-induced arrhythmia such as ventricular tachycardia and fibrillation, especially in the early period, and decrease the mortality. The mechanism is not clear and needs to be studied further. © 1994.