OBJECTIVE The relationship of plasma cytokine levels to infection, core temperature, and to one another in patients with thermal injury was examined. BACKGROUND The response to infection has been associated with cytokines such as interleukin 1 beta (IL1 beta), interleukin 6 (IL6), and tumor necrosis factor alpha (TNF alpha), and these cytokines have been studied in various inflammatory diseases. The authors previously reported that patients with thermal injury have elevated IL1 beta and IL6 plasma levels and that these cytokines may play different roles in the response to thermal injury. METHODS IL1 beta, IL6, and TNF alpha were measured by enzyme-linked immunosorbent assay (ELISA) in serial samples of plasma from 27 patients. RESULTS IL6 and TNF alpha levels were increased in severely infected patients as compared to patients who remained free of infection, and the IL6 level was higher in infected patients who died than those who survived. There was no apparent relationship between IL1 beta levels and infection. IL6 and IL1 beta were positively correlated with core temperature. The correlations between IL6 and IL1 beta, between IL6 and TNF alpha, and between TNF alpha and IL1 beta were significant. CONCLUSIONS These results suggest that IL6 and TNF alpha play a role in the response of burned patients to infection.