We considered as parameters of efficacy of G-CSF administration the duration of severe neutropenia (<0.5 G/L), and the prevalence of febrile neutropenia, and early infections. In our observation, no difference was observed in duration of severe neutropenia, but the incidence of febrile neutropenia was significantly decreased with early G-CSF, and this seems the most important clinical outcome. The gene discussed is CSF3; the disease is infection.