Granulocyte-macrophage colony stimulating factor (GM-CSF) and Interleukin-3 (IL-3) are increasingly used to stimulate granulopoiesis in neutropenic patients but these are rarely used in the lights of knowledge of the endogenous CSF-levels. In this study we measured serum levels of GM-CSF and IL-3 at diagnosis and after remission in children with acute leukaemia, using an enzyme linked immuno-sorbent assay (ELISA) techniques in 14 patients with acute myeloid leukaemia (AML) and 27 patients with acute lymphoblastic leukaemia (ALL). Twelve healthy age-matched children were used as a reference group. AML patients showed a highly significant increase in serum levels of GM-CSF and IL-3 before induction of therapy (p < 0.0001) compared to the reference control group, with a highly significant decline of both GM-CSF and IL-3 (p < 0.0001) after successful remission. On the other hand, ALL patients showed no significant elevation of GM-CSF and IL-3 at diagnosis (p > 0.5), with no significant difference between preinduction and postinduction serum levels of either (p > 0.5). Since these cytokines are known to be fundamental for the growth of AML cells, we postulate that the pretreatment levels of both GM-CSF and IL-3 could play a role in the pathogenesis of AML.