Using the latest second-generation mSEPT9 assay, we found a significantly higher sensitivity of mSEPT9 than CEA for the diagnosis of CRC patients (73.2% vs 48.2%; P < 0.001), especially for patients with stage II and III cancer (both P < 0.01), but a slightly lower specificity for the former (P > 0.05). The gene discussed is CEACAM5; the disease is colorectal carcinoma.