GNAS is a component of the heterotrimeric G-protein complex that has been shown to be mutated in 3-7% of colorectal cancers. Mutations at codon R201 of GNAS are typically activating mutations which have been described in various types of solid tumors. These mutations result in disruption of the intrinsic hydrolytic activity of Gsa, leading to constitutive activation. The clinical significance of these mutations in colorectal cancer remains to be established. Correlation with other clinical and laboratory findings is recommended.