The present study examined the acute effects of drugs that stimulate or block sympathetic nervous system activity on components of Type A behavior, affect, and cardiovascular responses to mental stressors. Either propranolol (a beta-adrenergic blocker), isoproterenol (a beta-agonist), or placebo was infused intravenously at different times in 12 healthy males. In two sessions, placebo (saline) was administered first, followed by a structured interview, challenging mental arithmetic test, and completion of affect scales. The procedure was then repeated with one of the active drugs, presented in counterbalanced order. Results indicated reliable drug effects on both heart rate (HR) and systolic blood pressure (SBP) reactivity to the tasks, with change scores to the tasks markedly increased by isoproterenol. Anxiety and hostility ratings paralleled results for HR and BP, with much of this effect being due to higher affect ratings for isoproterenol. The effect of the drugs on Type A behavior was unexpected, with global Type A and several components lowered by isoproterenol and unaffected by propranolol. These data are discussed in terms of the interfering effects of anxiety on Type A speech components. The influence of isoproterenol on affect and reactivity might reflect the physiologic action of a beta 2-adrenergic positive feedback loop which increases release of endogenous norepinephrine, and/or potentiating effects of emotion on reactivity to stress.