The role of G-CSF, GM-CSF and M-CSF in the treatment of AML and ALL was reviewed. These CSFs significantly accelerate the neutrophil recovery after intensive chemotherapy, and reduce febrile neutropenia and documented infections. There is no clear evidence that CSFs accelerate early regrowth of AML cells at the doses and schedules presently used clinically except one study. Patients who have received CSFs tend to have a higher CR rate, which does not seem to be translated into definite survival benefit. There has been no prospective randomized study showing any beneficial priming effect of CSFs on AML cells with better clinical outcomes.