In the last decade radioimmunoscintigraphy developed from an experimental approach to a clinically useful method. First promising results were obtained with Technetium-99m labelled murine monoclonal antibodies against carcinoembryonic antigen (CEA). Routine clinical application is restricted to colorectal carcinoma at the moment. Radioimmunoscintigraphy is recommended in case of recurring disease when conventional methods are ineffective or doubtful, especially in the pelvic region. The availability of monoclonal antibodies to new tumor-associated antigens will extend the spectrum to other gastrointestinal tumors. The possibility to generate recombinant humanized monoclonal antibodies and antibody fragments are encouraging new perspectives. These developments and the use of biological immune response modifiers to increase antigen expression could provide means to consider radioimmunotherapy of gastrointestinal cancers.