Plasma tumor necrosis factor (TNF) activity, cardiac index, extravascular lung water, systemic and pulmonary arterial pressures, pulmonary vascular resistance index, and arterial PO2 were monitored for 300 min in four groups of anesthetized pigs: saline-infused animals (n = 5), saline-infused animals given ibuprofen (12.5 mg/kg iv) at 0 and 120 min (n = 4), animals infused for 60 min with live Pseudomonas aeruginosa (Ps, 5 x 10(8) organisms/ml at 0.3 ml.20 kg-1.min-1, n = 6), and animals infused for 60 min with Ps plus ibuprofen administered at 0 and 120 min (n = 4). Infusion of Ps induced significant elevations (greater than 4-fold increase in units/ml of TNF by 60 min, P less than 0.05) in plasma TNF activity (L929 cytolysis assay) and alterations (P less than 0.05) in all hemodynamic and pulmonary parameters within 30-60 min. Ibuprofen administration in sepsis significantly decreased peak TNF activity by 2 units/ml and attenuated many of the physiological alterations due to sepsis. These results show that ibuprofen attenuates sepsis-induced injury and that alterations of acute septic insult are correlated with reduced plasma TNF activity in septic animals given ibuprofen.