BACKGROUND: Systemic inflammatory response after open heart surgery has an adverse effect on the postoperative course of patient, and results from the release of cytokines by leukocytes activated by cardiopulmonary bypass (CPB). TNF-alpha has an important role in inflammatory response-it has clinical effects such as fever, tachycardia, and hypotension, and also induces other cytokines. However studies about the change of blood concentration of TNF-alpha after CPB show differing results, and so have been up to now inconclusive, we have therefore endeavored to investigate the change of TNF-alpha level after CPB and its relationship with the postoperative course of patients. METHODS: We studied 20 children undergoing open heart surgery. Serum TNF-alpha was detected after induction (control), 5 minutes after onset of CPB (T1), 5 minutes after release of aortic cross clamp (T2), and 30 minutes after CPB (T3) by enzyme-linked immunosorbent assay. We compared the concentration of TNF-alpha and the duration that patients stayed in intensive care unit (ICU) and were supported by mechanical ventilator in group I (CPB time 60 minutes, n = 10). RESULTS: TNF-alpha levels of S2 and S3 were significantly lower than those of S1 and S4 (P = 0.001), but no difference was detected between group I and II. No statistical relationship was found linking TNF-alpha levels with the duration in ICU, or time supported by mechanical ventilator. Three children with postoperative complications showed higher level of TNF-alpha than others (P = 0.002). CONCLUSIONS: We concluded that TNF-alpha levels decreased during CPB, did not increased after CPB, and had no relationship to such postoperative courses as postoperative ICU time and intubation time, but there was a correlation with postoperative complications.