Burn injury induces a suppression of the Th1 response, which is associated with an increased susceptibility to conditions of infection, morbidity, and mortality. It is well established that cytokines modulate the pathogenesis of burn injury. In this study, plasma levels of interleukin-6 (IL-6) and interleukin-10 (IL-10) were determined in burn patients and correlated with the severity of sepsis. Sixty adult burn patients (total body surface area burned, 8-80%) were included in the study, of whom 34 developed sepsis and 14 died. The nonseptic group consisted of 26 patients. Thirty-one healthy blood donors served as controls. Patients were not treated with antibiotics until sepsis occurred. Plasma samples were collected immediately post-burn and after several days, and cytokine concentrations were determined by ELISA. Within three days, all the patients presented high levels of circulating IL-6, which were significantly higher in septic patients than in nonseptic patients (349±278 vs 63±56 pg/ml, p< 0.001). IL-10 levels were higher in septic patients than in nonseptic patients at all times in our study. The value of 60 pg/ml shows a sensitivity of 92% and a specificity of 93% in the differentiation of survivor from nonsurvivor septic patients. In this study the high value of circulating IL-10 on day 3 suggests that cytokine may discriminate between nonsurvivor septic and survivor septic patients.