AbstractGM‐CSF is a major regulator of myelopoiesis. Recombinant human GM‐CSF (250 μg/m2per day i.v.) was used prior to chemotherapy (“3 + 7” scheme) to recruit leukemia blasts in vivo (de novo AML patients, n = 20) into the chemotherapy sensitive phases of the cell cycle. The stimulatory effect of GM‐CSF on peripheral blood AML blasts was associated with a rapid redistribution of leukemia blood cells and with an increase in “S‐phase positive” cells. Standard induction chemotherapy (“3 + 7”) following GM‐CSF induced complete aplasia in 19/20 patients. In the same patients, rhGM‐CSF (given after chemotherapy) was found to shorten the time of complete aplasia compared to historical controls whereas post‐chemotherapy‐ and follow‐up data suggest no significant differences for CCR and survival. Together, our studies show that GM‐CSF can safely be administered to AML patients in combination with induction chemotherpay to recruit leukemia cells into the ce