Adrenomedulin (AM) is a novel peptide which has pronounced effects on the cardiovascular system (Kltamura e! al., 1993). The precise role of AM during myocardlal ischaemia is, however, unknown. The aim of this study was to determine if AM has a cardioprotective effect dunng myoeardial ischaemia. Pentobarbitone-anaesthetised rats were subjected to ligation of the left main coronary artery for 30 min followed by 120 min of reperfusion. Hearts were stained with Evan's blue and triphcnyltetrazolium chloride at the end of experiments for area at risk and infarct size measurement respectively. Animals were administered an i.v. bolus dose of Ah4 (0.5 ntn~lkg and 1 nmollkg) or saline 5 min preocclusion. Both doses of AM significantly reduced the number of ventricular ectoplc beats that occurred during ischaemia from 1339*116 to 521*116 and 520574 respectively (WO.05) and the incidences of VF from 66% to 26% and 27% respectively (IQO.05). Infarct size was significantly reduced from 34*3% to l&2% of area at risk in both AM treatment groups (WO.05). Prior to occlusion, AM (1 nmol/kg) induced a significant decrease in MABP (851% decrease, P<O.OS). These results show that AM exerts cardioprotection against Ischaemia-induced arrhythmias and myocardial injury.