Neopterin, a pteridine group compound that is secreted from macrophages is shown to be increased in adult leukemia; however there are few studies in childhood leukemia. This study aimed to investigate neopterin levels during childhood leukemia treatment and neutropenic fever episodes for the possibility of using as a marker for disease activity and differentiation of infections. A total of 44 children with acute leukemia, 19 children with infection (control group 1) and 21 healthy children (control group 2) were studied. Median serum neopterin level before induction chemotherapy (day 0) in 25 children (patient group 1) was significantly higher (27.7 nmol/L) than those at the beginning of 30 febrile episodes in 19 children in bone marrow remission (2.2 nmol/L) (patient group 2) and in control group 2 (0.4 nmol/L) (p< 0.05). It was (27.7 nmol/L) also significantly higher in control group 1 than in patient group 2 and control group 2 (p< 0.05). Serum neopterin levels at day 15 (2.1 mmol/L) and day 33 (0.4 mmol/L) of induction were significantly lower than day 0 of ALL subgroup at patient group 1. There were no significant difference in neopterin levels between days 0, 3 and 5 of neutropenic fever as well as between patients with microbiologically and/or clinically documented infections and those with fever of unknown origin in patient group 2 (p> 0.05). Serum neopterin did not show significant correlation with absolute neutrophil count and absolute monocyte count (p> 0.05). In conclusion, elevated neopterin at diagnosis of leukemia with decrement during induction therapy suggest that it might be an indicator of leukemic process; however larger studies for its role in identifying infections are warranted.