NRAS mutation is found in several cancers such as melanoma (13~25%), colorectal cancer (1~6%), lung cancer (1%), thyroid cancer (7%) and hepatocellular carcinoma (10%). It is know that the drug response against colorectal cancer medicine such as Erbitux and Cetuximab decreased and the prognosis of the metastatic colorectal cancer patient is bad if the patient has NRAS mutation. Recently, there are some papers that report the drug responses can be different for the NRAS mutation type so it is important to genotype each mutation. NRAS gene mutation genotyping test is necessary especially for predicting the drug sensitivity and prognosis. This test expected to play a major role for predicting the treatment of the patients and prognosis.