The treatment results in 13 patients with acute lymphatic leukemia are reported. All patients were treated according to the Hoelzer protocol. Granulocyte colony-stimulating factor (G-CSF) was administered till the onset of neutropenia and was continued as long as the leukocyte number increased above 3 x 10(9)/l. In phase I of Hoelzer's protocol G-CSF was administered on the average for 12 days, in phase II for 15 days. The chemotherapy of phase I was administered in scheduled time to 11 patients. In phase II the average delay against the scheduled time was 14 days. Reductions of dose were made only in 2 person. After finishing phase II 9 patients were in complete remission. Three patients died during therapy, one patient with small response died one month after completing phase II therapy. We believe that the administration of G-CSF only at the onset of leukopenia also abbreviate its duration as if the application were started immediately with the chemotherapy.