The combination of cyclophosphamide, doxorubicin, vincristine, and prednisone, given every 3 weeks (CHOP-21) is standard chemotherapy for aggressive lymphomas. To determine whether CHOP given every 2 weeks (CHOP-14) or the addition of etoposide (CHOEP-21, CHOEP-14) can improve results in patients ages 18 to 60 years with good prognosis (normal lactic dehydrogenase [LDH] level), 710 patients were randomized to 6 cycles of CHOP-21, CHOP-14, CHOEP-21 (CHOP plus etoposide 100 mg/m2 days 1-3), or CHOEP-14 in a 2 x 2 factorial study design. Patients in the biweekly regimens received granulocyte colony-stimulating factor (G-CSF) starting from day 4. Patients received radiotherapy (36 Gy) to sites of initial bulky disease and extranodal disease. CHOEP achieved better complete remission (87.6% versus 79.4%; P =.003) and 5-year event-free survival rates (69.2% versus 57.6%; P =.004, primary end point) than CHOP, whereas interval reduction improved overall survival (P =.05; P =.044 in the multivariate analysis). Although the CHOEP regimens induced more myelosuppression, all regimens were well tolerated. CHOEP should be the preferred chemotherapy regimen for young patients with good-prognosis (normal LDH level) aggressive lymphoma.