Application of monoclonal antibody for diagnosis and therapy of colorectal cancer was reviewed. The history and present status of radioimmunoimaging of cancer were presented. Immuno-guided surgery using radiolabeled antibody and hand-aided detector during surgery is a promising approach for complete excision of cancerous region. Also, a new antibody labeling method using a micro-magnet instead of radioisotopes may lead to a new era in immunodiagnosis of cancer. Finally, immunotargeting chemotherapy using antibody-anticancer drug conjugates was reviewed. A new type of immunoconjugate composed of human/mouse chimeric antibody and Neocarzinostatin seems to be one of the most promising drug formulas for immunotargeting chemotherapy.