Brain natriuretic peptide (BNP) is considered as a prognostic marker in patients with sepsis, but no data are available on BNP in pediatric cancer patients with febrile neutropenia (FN). Twenty-five pediatric cancer patients with FN were included in this study. Serum BNP level was measured. The mean BNP level was 330.8 +/- 765.3 pg/mL (5.9-3806 pg/mL). BNP levels of 12 patients were found over the normal level. High BNP levels were related to some conditions of the patients, and these were statistically significant (P < .05). These conditions were required erythrocyte suspension, had pneumonia, time stayed in hospital, and neutropenia time. When regression test was done, required erythrocyte suspension for anemia and had pneumonia were found to be statistically significant. In conclusion, this is one of the first studies on BNP levels in pediatric cancer patients with FN. However, further studies with large sample sizes are needed to confirm the results and provide new data about this issue.