We studied hemodynamic responses to - and -receptor agonists in 8 men to test the hypothesis that adrenoreceptor responsiveness is altered within 24 h of performing maximal exercise. Adrenoreceptor responsiveness was tested under two experimental conditions (with and without maximal exercise). Adrenoreceptor tests were performed 24 h after each subject performed graded upright cycle ergometry to volitional exhaustion. The two test days (experimental conditions) were separated by at least one week, and the order of exercise and no exercise conditions was counterbalanced. Steady-state graded infusions of phenylephrine (PE) and isoproterenol (ISO) were used to assess - and -adrenoreceptor responsiveness, respectively. Slopes calculated from linear regressions between ISO and PE doses and changes in heart rate, blood pressure, and leg vascular resistance for each subject were used as an index of - and -adrenoreceptor responsiveness. The slope of heart rate to ISO with maximal exercise was 1773 ± 164 beats/µg/kg/min compared to 1987 ± 142 beats/µg/kg/min without exercise (P = 0.158) while the slopes of vascular resistance to ISO were -438 ± 123 pru/µg/kg/min with maximal exercise and -429 ± 105 pru/µg/kg/min without exercise (P = 0.904). Maximxal exercise was associated with greater (P < 0.05) vascular resistance (15.1 ± 2.8 pru/µg/kg/min) and mean arterial pressure (15.8 ± 2.1 mmHg/µg/kg/min) responses to PE infusion compared to no exercise (9.0 ± 2.0 pru/µg/kg/min and 10.9 ± 2.0 mmHg/µg/kg/min, respectively). These results provide evidence that a single bout of maximal exercise increases ₁-adrenoreceptor responsiveness within 24 h without affecting -cardiac and vascular adrenoreceptor responses.