OBJECTIVE To study blood and bronchoalveolar lavage (BAL) fluid levels of platelet activating factor (PAF-acether) and phospholipase A2 (PLA2) in patients with septic shock or following severe trauma. METHODS Prospective controlled clinical study. METHODS An intensive care unit (ICU) of a university hospital. METHODS The study comprised 12 patients, 8 with septic shock and 4 with trauma, consecutively admitted to the ICU. Healthy volunteers were used as controls. RESULTS Blood PAF-acether and plasma PLA2 levels were measured within 24 h after the patients arrival to the ICU. The Apache II score and outcome were registered. Median values for PAF-acether and PLA2 in the septic shock patients were 10.5 x 10(-10) M and 5300 units/ml, respectively, whereas corresponding values in the trauma patients were 1.3 x 10(-10) M and 770 units/ml. Normal healthy individuals had no detectable PAF-acether in the circulating blood (< 0.5 x 10(-10) M), and normal plasma PLA2 activity was < 300 units/ml. Moreover, both PLA2 and PAF-acether levels correlated well with the severity of the disease as assessed by the Apache II scoring system (p < 0.01 for PLA2 and p < 0.05 for PAF-acether). In addition, PAF-acether and PLA2 were determined in BAL fluid of patients with septic shock (n = 5) and trauma (n = 3); increased PAF-acether levels were found in four patients with septic shock and one patient with trauma. CONCLUSIONS These results demonstrate a significant increase of both PLA2 and PAF-acether in the circulation of trauma patients, and a further increase in septic shock patients. It is possible that PAF-acether and PLA2 can be used as markers for the severity of the disease in septic shock and following severe trauma.