KRAS is a gene that encodes one of the several proteins in the epidermal growth factor receptor (EGFR) signaling pathway that is important in the development and progression of cancer. KRAS can harbor oncogenic mutations that yield a constitutively active protein. KRAS mutations are found in approximately 2-3% of esophageal cancers. In colorectal cancers, mutations in the KRAS gene may indicate poor prognosis and poor drug responses against anti-EGFR therapies. However, prognostic and predictive implications of KRAS mutations in esophageal cancers need to be fully elucidated. Results should be interpreted in conjunction with other laboratory and clinical findings.