The use of dobutamine as selective beta(1)-adrenoceptor agonist in in vivo studies on human thermogenesis and lipid utilization was investigated in 20 men. At 2.5, 5, and 10 microg x kg(-1) x min(-1), dobutamine induced significant increases in energy expenditure, lipid oxidation, and lipolysis. The beta(1)-adrenoceptor antagonist atenolol (bolus: 42.5 microg/kg, infusion: 1.02 microg x kg(-1) x min(-1)) blocked all dobutamine-induced effects on thermogenesis and lipid utilization. All parameters remained at levels comparable to those during saline infusion. The dose of atenolol used did not inhibit beta(2)-adrenoceptor-specific changes in energy expenditure, lipid oxidation, and lipolysis during salbutamol infusion (85 ng x kg(-1) x min(-1)). This indicates that atenolol was specific for beta(1)-adrenoceptors and did not camouflage concomitant beta(2)-adrenoceptor stimulation during dobutamine infusion. Therefore, we conclude that dobutamine can be used as a selective beta(1)-adrenoceptor agonist at dosages