Background: The Kyushu Study group of Clinical Cancer conducted a phase II study that evaluated the FIREFOX regimen. (KSCC0701, Akagi et al, J Clin Oncol 28:15s, 2010). This study demonstrated the efficacy and mild neurotoxicity of this regimen. The present study evaluated the efficacy and safety of the FIREFOX plus bevacizumab (bev). Methods: Eligibility criteria included histologically confirmed advanced colorectal cancer, ECOG PS 0-2 and adequate bone marrow, renal and hepatic function. Patients (pts) received an alternating regimen of 4 cycles of mFOLFOX-6 plus bev (oxaliplatin 85 mg/m², leucovorin 200 mg/m², bev 5 mg/kg d1 followed by 400 mg/m² bolus 5-FU and a 46-hr 2,400 mg/m² 5-FU infusion every 2 weeks) followed by 4 cycles of FOLFIRI plus bev (oxaliplatin replaced with irinotecan 150 mg/m² d1). This schedule was repeated until unacceptable toxicity or disease progression occurred. The primary endpoint is progression-free survival. (UMIN000001312) Results: Of the 52 pts enrolled from May 2008 to July 2009. Two of the patients did not fulfill the eligibility criteria. M/F, 30/20; median age, 59.5 years (range 37 - 75); ECOG PS 0/1/2, 46/4/0. The median number of administration cycles was 14 (range, 2 - 44). Response rate (RECIST criteria) for CR, PR, SD, PD and NE were 2 (4%), 28 (56%), 14 (28%), 4 (8%) and 2 (4%), respectively. An overall response rate was 60% (95% CI: 45 - 74%). Median progression-free survival was14.2 M (95% CI: 10.6 M-16.3 M) and median overall survival was 27.5 M (95% CI; 22.4 M – not determined). The 2-year survival rate was 56.8%. Of the 52 pts evaluated for toxicity. The most common grade 3-4 adverse events were leukopenia (7.7%), neutropenia (32.7%), anemia (1.9%), fatigue (9.6%), anorexia (13.5%), stomatitis (3.8%), neurotoxicity (3.8%), hypertension (1.9%), diarrhea (7.7%), febrile neutropenia (3.8%), nausea (9.6%), vomiting (5.8%), hypersensitivity (3.8%), and thromboembolism (1.9%). Conclusions: The results of this phase II study show that the FIREFOX plus bev regimen is effective and well tolerated in the first-line treatment of advanced colorectal cancer. The low rate of neurotoxicity is also promising.