15 children with ALL and chemotherapy related neutropenia were treated with GM-CSF (Leucomax-Sandoz/Schering-Plough) in a dose of 5 micrograms/kg b.w./day during 7-10 days. Altogether 21 cycles were performed. Increase in the number of neutrophils in the majority of cases was observed already after 3 days of GM-CSF administration. The median time of neutropenia recovery was shorter in children treated with GM-CSF than in the control group. The frequency of severe infections was also significantly lower. No serous side effects were observed.