Background: The mutational landscape of metastatic colorectal cancer (CRC) is being elucidated by next-generation sequencing of both primary tumors and metastatic foci. In this study, we examined the results of all stage IV CRC cases submitted to our molecular tumor board (MTB). Methods: We performed a retrospective analysis of all patients who had next-generation sequencing performed between January 2015 and August 2017 on either their primary tumor and/or metastasis. Cases were presented at a MTB convened twice monthly. For the purposes of this study only pathogenic mutations were notated, not variants of unknown significance (VUS). Results: Eighty-seven unique patients had 97 specimens sequenced (28 primary tumors and 69 metastases). The primaries averaged 3 mutations per specimen (range: 1-6) whereas the metastases averaged 4 (range: 1-14, p=.25). The most common anatomic sites of submitted metastatic tissue were the liver (n=35, average mutations=4), followed by the lungs (n=10, average mutations=3) and the omentum/peritoneum (n=8, average mutations=3). Two patients had both a primary tumor and a metastasis sequenced, with a 33% rate of concordance in inter-specimen mutations. Five patients had multiple metastases sequenced, with a 53% rate of concordance in inter-specimen mutations; in every case of longitudinal sequencing, mutational burden increased in metastases over time. The most common mutation was apc (21% of all mutations), followed by p53 (16%) and then kras (13%). Candidacy for EGFR-directed therapy was found in 8 cases, and mismatch repair defects were detected in 5 cases. Conclusions: In stage IV CRC cases sent to our MTB, tissue from metastases was more commonly submitted for analysis than from the primary tumors. There is not necessarily concordance between mutations in primary tumors and metastases, nor among multiple metastases in the same patient. Sequencing at multiple time points in the disease course may allow observation of clonal evolution and dynamic adaptation of therapeutic targets.