Age is an important prognostic parameter, especially in patients with advanced high-grade non-Hodgkin's lymphoma (HG-NHL) who require more intensive and extensive therapy for any possible chance of cure. We investigated the potential of granulocyte colony-stimulating factor (G-CSF) for reducing myelotoxicity, which is the most important dose-limiting factor for chemotherapy. Between March 1993 and June 1995, 158 previously untreated patients 60 years and older with HG-NHL were included in a cooperative randomized comparative trial and treated with a combination therapy including VNCOP-B (cyclophosphamide, mitoxantrone, vincristine, etoposide, bleomycin, and prednisone) with or without G-CSF. G-CSF was administered at 5 microg/kg/d throughout the treatment starting on day 3 of every week for 5 consecutive days. Of the 158 patients registered for the trial, 149 patients were evaluable: 77 received VNCOP-B plus G-CSF and 72 received VNCOP-B alone. The overall response rate was 81.5%, with complete response in 59%: 60% in the VNCOP-B plus G-CSF group, and 58% in the VNCOP-B group. At 30 months (median 24 months), 68% of all complete responders were alive without disease in the G-CSF group and 65% in the control group. Neutropenia occurred in 18 out of 77 (23%) of the G-CSF treated patients and in 40 out of 72 (55.5%) of the controls (P = .00005). Clinically relevant infections occurred in 4 out of 77 (5%) of the G-CSF group and in 15 out of 72 (21%) of the controls (P = .004). The delivered dose intensity was higher in patients receiving G-CSF (95% v 85%), but the difference was not statistically significant. Our data show that VNCOP-B is a feasible and effective regimen in elderly HG-NHL patients, and that the use of G-CSF reduces infection and neutropenia rates without producing any significant modifications to the dose intensity, CR rate, and relapse-free survival curve.