Dopexamine hydrochloride is a novel compound with properties of DA1-dopaminergic and beta 2-adrenergic receptor agonism and neuronal noradrenaline uptake inhibition. It has been shown to produce beneficial renal and haemodynamic effects in patients with severe heart failure. We compared the haemodynamic effects of dopexamine (0.5 to 6 micrograms/kg/min) with those of dobutamine (5 to 25 micrograms/kg/min) in 9 patients with severe congestive heart failure. The two drugs were similar in their effects at peak infusion rates: heart rate increased (dopexamine 87 +/- 17 to 100 +/- 14; dobutamine 91 +/- 18 to 103 +/- 17 min-1), cardiac index increased (dopexamine 1.7 +/- 0.5 to 2.8 +/- 1.1; dobutamine 1.8 +/- 0.5 to 3.0 +/- 1.1 l.min-1.m-2) and systemic vascular resistance decreased (dopexamine 1553 +/- 221 to 1117 +/- 432; dobutamine 1721 +/- 347 to 1280 +/- 433 dyne.s.cm-5). Neither drug affected pulmonary artery wedge pressure (dopexamine 24 +/- 6 to 22 +/- 6; dobutamine 25 +/- 9 to 24 +/- 10 mm Hg). Dopexamine had significantly lower peak effects on left ventricular stroke work index (dopexamine 20 +/- 9, dobutamine 27 +/- 15 g.m.m-2, P less than 0.05) and cardiac power output (dopexamine 0.71 +/- 0.36, dobutamine 0.93 +/- 0.46 W, P less than 0.05). These haemodynamic effects, due largely to vasodilatation but with some contributory positive inotropy, indicate that dopexamine will be useful in the acute treatment of congestive heart failure.