Imacis-1 is a combination of F (ab')2 antibody fragments, of two monoclonal antibodies, anti-CEA and 19.9, radiolabelled with Iodine-131. Thirteen patients with 14 tumours (eight pancreatic, six colorectal) were imaged to evaluate the ability of this radiopharmaceutical to detect both pancreatic and colorectal cancer. Positive tumour uptake was demonstrated by external gamma camera imaging in six patients with pancreatic cancer and in three with colorectal cancer. The results of this preliminary study confirm the ability of this antibody cocktail to localise in colorectal cancer and suggest that it may be of value in the detection of pancreatic cancer.