From September 1988 two hundred-sixty-seven (267) untreated patients (pts) with stage II to IV high grade non Hodgkin's lymphoma (NHL) have been enrolled in a multicenter, randomized, still ongoing study, comparing two third-generation combination chemotherapy regimens, MACOP-B versus F-MACHOP. At the present time, 177 pts have completed the treatment program and are evaluable, with a median follow-up of 13 months. Clinical, histologic and laboratory characteristics are equally distributed in both groups. Among the 92 pts treated with MACOP-B, 58 (63%) achieved a complete remission (CR), 17 complete responders have relapsed (29%), and 21 have died (23%), including 3 treatment-related deaths. Among the 85 pts who received F-MACHOP, 65 (76%) achieved a CR, 9 complete responders have relapsed (14%), and 11 pts have died (13%), including 3 treatment related deaths. 30 months-projected survival is 64% for MACOP-B treated pts compared to 84% for F-MACHOP treated pts; 30 months-projected relapse- free survival is 80% and 84%, respectively. F-MACHOP seems to be superior in immunoblastic lymphoma (overall survival, OS, 82% vs. 54%) and in Burkitt-type lymphoblastic lymphoma (OS 100% vs, 42%). The degree of hematological and non-hematological toxicity was similar in both regimens. More reliable conclusions will be drawn after a longer follow-up.