Background: Recent investigations have demonstrated gender related immunologic alterations after trauma. These complications arise due to polymorphonuclear granulocytes (PMN) interacting with endothelium via l-selectin. Therefore, the purpose of this study was to investigate gender related differences in the expression of l-selectin in relation to posttraumatic multiple organ dysfunction syndrome (MODS). Methods: Multiply injured patients were prospectively entered in the study. MODS was determined using the Denver score. The concentration of l-selectin on the surface of PMN was determined using flow cytometry during a 14 days' period. Results: 48 patients were included in the study. The kinetics of l-selectin were different comparing male and female patients. Male patients with MODS initially showed a rapid decrease of surface l-selectin from 80 to 20ng/ml. A return to admission levels was related to MODS. Male patients without MODS displayed elevated l-selectin levels up to 140ng/ml. Female patients, however, all showed an initial rapid decrease of l-selectin to 20ng/ml. Women who developed posttraumatic MODS had significantly increased levels up to 110ng/ml before development of MODS developed. Conclusions: We feel that a gender related dimorphism in the initial l-selectin expression following trauma exists and is associated with MODS. These findings indicate new therapeutic means for the treatment of MODS. Therapies should be timely and gender dependently coordinated.