As the most commonly reported cancer in Australia and the third most common cancer worldwide, colorectal cancer (CRC) represents a complex disease, for which effective therapies are urgently required. Activation of the EGFR MAPK signalling pathway, either through EGFR over-expression or mutation, or through mutation of key MAPK signalling components such as KRAS and BRAF, has been shown to play an important role in CRC tumour initiation and progression, and anti-EGFR therapeutics represent the most advanced treatment option for metastatic CRC patients. However, given the complexity of the MAPK and associated signalling pathways, targeting a single component may not always be effective. Recent evidence that the widely prescribed diabetes therapeutic, metformin, may both confer a therapeutic advantage to CRC patients and affect downstream EGFR pathways through its action as an AMPK activator, presents a unique opportunity to characterise the intersection between RAS/RAF/MAPK and metabolic signalling downstream of EGFR. We have assessed the efficacy of metformin treatment in a large panel of CRC cell lines, in an effort to identify a subset of patients that may benefit from metformin treatment, either singly, or in conjunction with anti-EGFR therapeutics. Gene expression signatures of sensitive and resistant cell lines have been compared and stratified, both at a basal level and in response to metformin treatment, and metabolic profiles have also been determined. Additionally, we have used a panel of isogenic CRC cell lines to determine whether mutations in KRAS or BRAF affect susceptibility to metformin treatment, as has previously been shown in other cancer settings.