PURPOSE: Contemporary chemotherapy has significantly improved the event-free survival (EFS) among patients with T-cell disease. However, myelosuppression has been a significant adverse effect of this approach. In this study, we assessed the impact of r-metHu granulocyte colony-stimulating factor (G-CSF) on the period of neutropenia, number of days of hospitalization, and delays in subsequent administration of chemotherapy in a cohort of patients with T-cell leukemia (T-ALL) or advanced stage lymphoblastic lymphoma (ASLL). PATIENTS AND METHODS: This open-label, randomized trial incorporated r-metHuG-CSF into the induction and two consecutive continuation-therapy cycles of our intensive program for T-cell malignancies. In the induction phase, r-metHuG-CSF was given after two different combinations of chemotherapy, one of which included vincristine, prednisone, cyclophosphamide, and adriamycin and the other a continuous infusion of high-dose ara-C and L-asparaginase. In the two continuation-therapy cycles, r-metHuG-CSF was given following the combination of vincristine, adriamycin, prednisone, and 6-mercaptopurine (MP) and after continuous infusion of high-dose cytarabine (ara-C). RESULTS: Fifty-six patients with T-ALL and 33 with ASLL were enrolled onto study from April 1994 to December 1995. Our data show no significant difference in number of days of absolute neutrophil count (ANC) less than 500/microL, hospitalizations, or delays in therapy in the induction phase. However, in the continuation-therapy phase the number of days of ANC less than 500/microL was significantly shorter (P = .017) on the G-CSF-arm without significantly affecting the number of days of hospitalizations or delays in therapy. CONCLUSION: r-metHuG-CSF did not significantly affect the period of neutropenia, hospitalization, or delays in therapy in the induction phase, whereas in the two cycles of continuation therapy, it significantly shortened the period of neutropenia.