The extensive study of genetic alterations in colorectal cancer (CRC) has led to molecular diagnostics playing an increasingly important role in CRC diagnosis and treatment. Currently, it is believed that CRC is a consequence of the accumulation of both genetic and epigenetic genomic alterations. It is known that there are at least 3 major pathways that lead to colorectal carcinogenesis: (1) the chromosomal instability pathway, (2) the microsatellite instability pathway, and (3) the cytosine-phospho-guanine island methylator phenotype pathway. With recent advances in CRC genetics, the identification of specific molecular alterations responsible for CRC pathogenesis has directly influences clinical care. Patients at high risk for developing CRC can be identified by genetic testing for specific molecular alterations, and the use of molecular biomarkers for predictive and prognostic purposes is also increasing. This is clearly supported by the recent advances in genetic testing for CRC whereby specific molecular alterations are identified for the purpose of guiding treatment with targeting therapies such as anti-endothelial growth factor receptor monoclonal antibodies.