In normally active individuals, postexercise hypotension after a single bout of aerobic exercise is due to an unexplained peripheral vasodilation. Prostaglandin production has been suggested to contribute to the increases in blood flow during and after exercise; however, their potential contribution to postexercise hypotension has not been assessed. The purpose of this study was to determine the potential contribution of a prostaglandin-dependent vasodilation to changes in systemic vascular conductance underlying postexercise hypotension by inhibiting production of prostaglandins with the cyclooxygenase inhibitor ibuprofen. We studied eleven healthy normotensive men (aged 23.7±4.2 yr) before and through 90 min after a 60 min bout of cycling at 60% VO_2peak on a control and a cyclooxygenase inhibition day (randomized). Subjects received 10 mg/kg of oral ibuprofen on the cyclooxygenase inhibition day. On both study days, arterial blood pressure (automated auscultation) and cardiac output (acetylene uptake) were measured and systemic vascular conductance was calculated. Inhibition of cyclooxygenase had no effect on baseline values of mean arterial pressure or systemic vascular conductance (P > 0.2). After exercise on both days, mean arterial pressure was reduced (control -2.2 ± 1.0 mmHg; ibuprofen -3.8 ± 1.5 mmHg, both P < 0.05 vs. preexercise) and systemic vascular conductance was increased (control 5.2 ± 5.0%; ibuprofen 8.7 ± 4.1%, both P < 0.05 vs. preexercise). There were no differences between study days (P > 0.6). These data suggest a prostaglandin-dependent vasodilation does not contribute to the increased systemic vascular conductance underlying postexercise hypotension.