Background: Efficacy and safety of FOLFOX{Bi-weekly cetuximab as first-line therapy for patients with nonresectable metastatic colorectal cancer (mCRC) were examined. Methods: The multicentre phase II trial had began from September 2011. Inclusion criteria were an age of 20 years or older, adenocarcinoma of the colon or rectum, first occurrence of metastatic disease with KRAS wild type tumor that could not be resected, performance status score (ECOG) of 1 or less, and adequate hematologic, hepatic, and renal function. Patients received mFOLFOX6/Cetuximab 500 mg/‡u/biweekly 120min until PD, unacceptable adverse effects, or withdrawal of consent occurred. In the event of grade 2 adverse effects, suspension of Oxaliplatin only was permitted. Primary endpoint was Response Rate, secondary endpoint was anti-tumor effect at week 8, PFS, OS, safety, and efficacy of 5-FU{LV{Cetuximab therapy. Results: 60 patients were screened and 59 underwent the treatment by March 2013. Age 64.5 (38-82), male/female: 47/13, PS 0/1: 51/9, rectal/colon: 31/29 and metastasis in liver/lung/ lymph node/ the other: 51/15/19/7. Data had been analyzed to date showed high response rate, 64% with disese control in 96% -PR 38pts (64%), SD 19 pts (32%). Incident rate of grade 3 or 4 adverse events were neuropenia 19%, peripheral sensory neuropathy 4.8% and rash 8.1%. Conclusions: FOLFOX{Bi-weekly cetuximab therapy benefited in safety administration with high response rate. Therefore it can be considered as a beneficial treatment. Clinical trial information: UMIN000006402.