We previously reported that a combination of HU, FA and 5FU was better than FA + 5FU (RR: 30% vs 22%; ASCO 463,1992). From January 1992,237 pts with histological diagnosis of ACRC, with evidence of advanced disease, not previously treated with chemotherapy, were randomized between arm A: I-FA (250mg/m 2 in a 2 hour IV infusion) and 5FU (600mg/m 2 IV bolus, 1 hour after FA) plus HU (3000mg, day I, given per os in three administrations, every 8 hrs, 6 hrs after 5FU) or arm B: FU (600mg/m 2 IV bolus) plus HU as arm A and IFN (3×10Ul/m 2 , sc three times a week). On both arms treatment was given weekly for 6 wks followed by a 2 wk rest period. At the time of this analysis, a total of 203 (86%) pts. are evaluablefor response: 102 (86%) and 101 (86%) in arms A and B respectively. The analysed patients are comparable for median age (63 vs 63), sex (M:66 vs 61, F: 36 vs 40), PS (100&–80: 89 vs 88; 70–60%: 13 vs 13). Preliminary analysis shows the following results: on arm A 28 (28%) CR + PR, 45 (44%) NC, 29 (28%) P and on arm B 8 (8%) CR+ PR, 41 (41%) NC, 52 (51%) P. Diarrhea, mucositis and vomiting are the most frequent non-haematological side effects in both arms. Two pts died due to severe gastrointestinal toxicity (diarrhea and mucositis) one on each arm.