Burn patients with intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) undergo vigorous resuscitation and accumulate peritoneal fluid (PF) that is a plasma ultra-filtrate. This study compared antithrombin (AT) and cytokine levels in burn patient plasma and peritoneal fluid (PF).Twenty-nine patients were studied; 22 developed IAH and 9 progressed to ACS. Burn+inhalation injury was present in 22 patients; 5 had burn only and 2 had inhalation only. Sixteen patients died; of these, 9 survived less than 48h due to the severity of their injuries. Flow cytometry utilized the Cytometric Bead Array kit for Human Th1/Th2 cytokines. AT levels were determined by the Accucolor method spectrophotometrically.All cytokine levels were significantly elevated in burn plasma and PF compared to normal plasma, p<0.001. AT plasma levels were decreased compared to normal. AT and cytokines were present in peritoneal fluid of burn patients with IAH and ACS. Patients who died had decreased plasma levels of AT and increased IFN-γ, IL-10, IL-6, IL-4, IL-2 peritoneal fluid levels compared to survivors.Peritoneal fluid may be a reservoir for cytokines during initial resuscitation and contributes to homeostatic perturbations in burn patients.