Background: Cetuximab improves benefit in patients with kras wild type when added to CT for mCRC (Crystal, opus, celim trials). In order to assess the safety and efficacy of cetuximab in daily-practices a national prospective observational multicenter study was performed. Methods: Physicians (n=94), in health institutions (44 public and 46 private hospitals, 4 cancer centers) enrolled prospectively 502 patients. The eligibility criteria were kras wild type mCRC treated with cetuximab in combination with CT as first-line regimen and at least one measurable lesion. Data are available at 3 months, for 496 patients enrolled between september 2009 to march 2012. Results: Mean age 65,7 years old, 62.9% male, ECOG score 0-1 88.1%, 2-3 11.9%, metastases site were liver 70%, lung 26% and others unlimited 39%. Resectable mCCR 10.6%, potentially resectable metastases 33.9% and unresectable 55.5%. Primary tumor location colon: right 20.9%, transverse 6%, left 35.3%, rectum 30.5%, others 7.3%. Primary cancer was resected in 66 % (n=332), 25% (n=125) received adjuvant CT. Cetuximab was administrated respectively every week(20.2%) or two weeks (79.8% of patients). CT regimens were folfiri 51.8%, folfox 4 36.5%, others 11.7%. At 3 months response rate was complete in 4.6%, partial 44.9%, stable 34%, progression disease 16.5%. Reasons for specific cetuximab treatment discontinuation (n=207) were progressive disease 35.3%, therapeutic break 23.2%, all grade cutaneous toxicity and allergic reaction 15.9%, patient request 2.9%, surgery recruitment 20% radiotherapy, radiofrequency and others 2.7%. Adverse events in grade 2 and 3-4 were respectively neutropenia (9.4%;7.9%), anemia (8.5%;1.4%), thrombocytopenia (2.6%;1%), diarrhea (10.8%;5.3%) vomiting (5.3%;2.2%), folliculitis (17.9%;3%), xerosis (13.3%;2%), paronychia (5%;0.9%), allergy 3.4%. Conclusions: Values reported are consistent with those previously identified trials and can better understand the reasons of drug stopping. The study continues to evaluate prognostic factors influencing response, toxicity and drug discontinuation.