OBJECTIVES: Colorectal cancer is the third most common cancer in Wales, with 2444 new cases reported in 2012. Incidence increased by 28.5% between 2002 and 2012. While survival rates in colorectal cancer are improving globally, the UK continues to lag behind other major economies. Recent evidence demonstrates that cetuximab can result in significant life extension when added to chemotherapy as a first line treatment of RAS wild type metastatic colorectal cancer. At present, cetuximab is funded in Wales mainly through Individual Patient Treatment Requests which are increasing in number due to the rising demand from both patients and physicians. An evidence submission was submitted to AWMSG to highlight this clinical benefit and assess the cost effectiveness of cetuximab.  METHODS: An economic model was developed to assess the cost effectiveness of cetuximab in the management of unresectable RAS wt metastatic colorectal cancer in comparison to comparators available in the Welsh NHS; FOLFOX, FOLFIRI, or CAPOX alone. This includes a small population of patients with metastases confined to the liver who may subsequently be eligible for curative resection after treatment with cetuximab plus chemotherapy. The time horizon is 10 years and the discount rate applied to both outcomes and costs is 3.5%. Cetuximab Welsh Patient Access Scheme (WPAS) price was used in all analyses and the dose was set to fortnightly dosing as typically prescribed in Wales. RESULTS: Economic analyses estimated an incremental cost effectiveness ratio of £29,512 per QALY gained for cetuximab + FOLFOX compared to FOLFOX alone and £35,731 per QALY gained for cetuximab + FOLFIRI compared to FOLFIRI alone.  CONCLUSIONS: These analyses demonstrate that cetuximab is a cost effective treatment and a good use of NHS Wales resources through stratification of RAS wild type patients who are likely to respond to treatment and offer patients a life-extending treatment option.