We investigated whether a brief ischaemic episode (ischaemic pretreatment) preconditioning might attenuate the acute cardiotoxicity of the anthracycline, epirubicin. Isolated rat hearts perfused at a constant flow rate of 10 ml/min, were preconditioned with 5 min. of global ischaemia and 10 min. of reperfusion (preconditioned hearts), or were perfused for 15 min. (control hearts). The hearts were then subjected to 20 min. of infusion with epirubicin (2 mg/ml) or vehicle by a side arm of the perfusion system at a rate of 0.1 ml/min. (0.2 mg epirubicin/min.). Attenuation of cardiotoxicity of a total dose of 4 mg of epirubicin was assessed by functional and metabolic parameters during infusion and during the following 30 min. recovery period. Cardiotoxic effects were reduced in preconditioned hearts compared to control hearts. Thus left ventricular developed pressure and heart rate product after 20 min. of epirubicin infusion was depressed to 27 +/- 7% (mean +/- S.D.) and 40 +/- 4% (mean +/- S.D.) of baseline values in the control group and the preconditioned group, respectively (P < 0.05). Furthermore, we observed less contracture during epirubicin infusion and more effective reversal of contracture during the recovery period in the preconditioned hearts. Improvement in cardiac function was associated with a significantly lower (P < 0.05) myocardial content of epirubicin in the preconditioned group at the end of the infusion period. We conclude that ischaemic preconditioning attenuates the acute cardiotoxicity of epirubicin, probably by reducing the myocardial accumulation of the anthracycline.