[en] A radiolabelled monoclonal antibody was injected intravenously into two patients with disseminated carcinoma of the colon and serial scintigrams were obtained on three consecutive days. In addition to the specific antibody image, blood pool and conventional liver scans were also obtained. After computer-based subtraction discrete hepatic metastases could be demonstrated in both patients, while in the second patient, the primary colonic tumour was also visualised for the first time. The study demonstrates the specific localisation of primary and secondary carcinoma of the colon with a radiolabelled monoclonal anti-tumour antibody and offers an improved method of specifically detecting tumours in man