We showed previously that reperfusion causes hypercontracture and cell death of cardiomyocytes due to oscillatory elevations of cytosolic Ca2+ originating from the sarcoplasmic reticulum (SR) and that inhibition of the latter prevents reperfusion-induced cell death. It has also been shown that mitochondrial permeability transition (MPT) induces cell death in reperfused myocardium. We now investigated in isolated cardiac cells from adult rat if SR- triggered Ca2+ oscillations and MPT are causally connected in signalling towards reperfusion-induced cardiomyocyte hypercontracture and cell death. During simulated ischemia, no significant induction of MPT, i.e. mitochondrial dysfunction was observed, however, reperfusion induced a marked induction of MPT and concomitantly, cells developed hypercontracture. Pharmacological inhibition of MPT, of SR-Ca2+ release, or of mitochondrial Ca2+ uptake significantly reduced the extent of MPT induction and hypercontracture. We conclude that induction of MPT is involved in the development of reperfusion-induced death of reperfused cardiac myocytes. It is triggered by oscillations of cytosolic Ca2+ originating from the SR.