PURPOSE: We studied hemodynamic responses to α- and β-receptor agonists in 8 healthy normotensive men on two different test days, each separated by at least one week, to test the hypothesis that adrenoreceptor responsiveness is altered within 24 h of performing a single bout of maximal exercise. METHODS: On one day, adrenoreceptor responsiveness was tested 24 h after each subject performed graded upright cycle exercise to volitional exhaustion. On another day, testing for adrenoreceptor responsiveness was repeated with no exercise (control). The order of exercise and control treatments was randomized and counterbalanced. Steady-state infusions of isoproterenol (ISO) were given at rates of 0.005, 0.01, and 0.02 μg/kg/min. Infusions of phenylephrine (PE) were given at rates of 0.25, 0.50, and 1.00 μg/kg/min. Slopes calculated from linear regressions between ISO and PE doses and changes in heart rate, blood pressure, and leg vascular resistance (occlusion plethysmography) for each subject were used to assess α- and β-adrenoreceptor responsiveness. RESULTS: Compared to control, exercise did not alter the slopes of heart rate (1987 ± 142 vs. 1773 ± 164 beats/μg/kg/min; t = 1.014, P = 0.331) and vasodilation (−429 ± 125 to −438 ± 140 pru/μg/kg/min; t = 0.015, P = 0.0908) to ISO infusion. In contrast, exercise was associated with greater (t = 6.323, P = 0.040) vascular resistance (15.1 ± 2.8 pru/μg/kg/min) and mean arterial pressure (18.6 ± 4.4 mmHg/μg/kg/min) responses to PE infusion compared to the control condition (9.0 ± 2.0 pru/μg/kg/min and 10.2 ± 2.3 mmHg/μg/kg/min, respectively). CONCLUSION: Our results provide evidence that a single bout of maximal exercise increases α1-adrenoreceptor responsiveness without affecting β1-cardiac and β2-vascular adrencoreceptor responses. Supported by the National Aeronautics and Space Administration.