Although early beta-blockade in acute myocardial infarction (AMI) may have potential benefits owing to an anti-arrhythmic effect and limitation of infarct size, the haemodynamic effects are not well characterised. Accordingly, we studied the effects of intravenous beta-blockade by sotalol in AMI, commencing a mean of 6 hours after the onset of chest pain, with particular reference to systemic haemodynamic changes and left ventricular (LV) volumes. Thirty patients were randomised to a control group or to sotalol therapy starting with 40 mg and increasing to 120 mg, followed by the maximal dose tolerated every 6 hours for 72 hours. Sotalol reduced heart rate and mean blood pressure without elevating pulmonary wedge pressure or increasing enzymatic infarct size. Sotalol also decreased the incidence of ventricular tachycardia (P less than 0.001). An important new finding was that there was no increase in the LV volume measured by radionuclide techniques. Therefore intravenous sotalol safely achieved its beneficial effects without causing LV dilatation.