Patients: Our study will enroll consecutive subjects participating in the health check-up at National Taiwan University Hospital (Health Management Center), who will undergo I-FOBT, G-FOBT, HpSA, colonoscopy and EGD. The diagnostic values of three fecal testing, alone or in combination, will be respectively evaluated. knowing that subjects who were detected with gastrointestinal tract cancers might be small based on one screening setting, we also recruited patients who were detected with gastrointestinal tract cancers at other screening sites and were referred to the National Taiwan University Hospital for confirmatory diagnosis and treatment. They were also requested to complete the three fecal tests as well as the bidirectional endoscopies; however, it should be noted that, in this group of patients, those who completed only one of the bidirectional endoscopies were still eligible.