The present study has investigated the effects of dobutamine on postischaemic dysfunction in the setting of global ischaemia and reperfusion in a model of isolated heart preparation. Isolated rat hearts were subjected to 20 min of zero-flow global ischaemia followed by 45 min of reperfusion. Dobutamine administration (10 microg/kg/min) during the reperfusion period resulted in deterioration of functional recovery, which was abolished by propranolol administration. Long-term thyroxine pretreatment (12.5 microg 100 g(-1) body weight, b.i.d., s.c., for 2 weeks) reversed the detrimental effect of dobutamine and increased postischaemic recovery of function. We conclude that the combination of thyroxine pretreatment and dobutamine administration could potentially be a new therapeutic strategy to improve postischaemic dysfunction particularly in clinical settings such as cardiopulmonary bypass and/or myocardial infarction.