The aim of the present study was to investigate the effects of crocin - a natural antioxidant derived from saffron - on cardiac reperfusion-induced arrhythmia and antioxidant systems such as catalase and superoxide dismutase (SOD) enzyme activities, glutathione (GSH) and malondialdehyde (MDA, as a marker of lipid peroxidation) levels. Rats in 4 experimental groups were administered crocin (20 mg/kg/day) or vehicle (i.p.) for 21 days with or without cardiac ischemia-reperfusion (IR). At the end of this period, hearts of anaesthetized animals in IR and "Cr + IR" groups were subjected to 10 min occlusion of the left anterior descending coronary artery and thereafter reperfused for 30 min. The results suggest that crocin is partially capable of suppressing reperfusion-induced arrhythmias. Compared to control group, ischemic-reperfusion injury significantly decreased SOD activity and GSH level and increased MDA level of heart muscle. "Cr + IR" group showed remarkably increased catalase activity in heart tissue (28.7 ± 6.6 vs. 23.6 ± 4.1 U/mg protein, P < 0.05) compared to the IR group. The level of cardiac tissue SOD activity in the "Cr + IR" group animals did not decline significantly compared to rats that were administered crocin alone with no ischemia. The results suggest a protective role of crocin on cardiac reperfusion arrhythmias which may at least partially be related to stability or even amplification of antioxidant systems. Crocin may potentially be useful for treatment or prevention of arrhythmias in patients with ischemic heart disease and this issue remains to be investigated in future clinical studies.