We hypothesized that the conventional ProMACE-CytaBOM regimen could be improved by administering all drugs on d1 with the S-phase agents first in the sequence, prednisone d2-6 only, increasing doxorubicin to 50 mg/m2, and adding G-CSF d2-13 to ameliorate neutropenia. This regimen was tested in a Phase I study of 20 patients (pt) with non-Hodgkin's lymphoma (NHL). The median age was 61 yrs (range, 29-79). Four pt had low grade and 16 intermediate/high NHL. The International Prognostic Index was low in 6 cases, low-intermediate in 12, and high-intermediate in 2. Twelve pt received > or =6 cycles; 4 had 5 cycles, 3 had 4 cycles, and 1 received only 1 cycle. Sixteen pt received subsequent cycles without delay. The response rate was 95% (19/20) with 12 CR and 7 PR; one pt progressed during treatment. After a median follow-up of 30 months, 85% (17/20) remain alive. This higher dose ProMACECytaBOM regimen can be given to older adult patients in an outpatient setting. Phase III studies would be required to determine if it produces a superior overall survival compared to other regimens.