A number of tumour ma rkers have been identified in patients with gastrointestinal malignancies. Although these markers have limited clinical application, a knowledge of their use and shortcomings will help prepare for newer applications in gastrointestinal oncology. Tumour markers recently have been used as a serological means of monitoring gastrointestinal malignancy for recurrence and have been studied experimentally by radionuclcotidc imaging using radiolabelled markers. More recently, the use of tumour antigens as specific cancer vaccines has attracted the attention of gastrointestinal oncologists as therapeutic agents.