All patients greater than 18 years old who have had a prior resection of colorectal cancer and are suspected of having recurrent disease.

Rising serum CEA levels greater than 6 on two successive tests.

Resectable residual or recurrent disease. Patients in the occult arm (Arm 1) must have no visible residual disease in the abdomen at the time of the last surgical exploration. In addition, there must be no imageable definitive site of recurrent disease using conventional imaging modalities including; CT scan of chest/ abdomen/ pelvis with contrast, MRI scan, and chest x-ray. Patients in arm 2 may have a single site of recurrent or metastatic disease which is resectable but in whom additional sites of disease are not known and no imageable disease other than a solitary site of potentially resectable disease is identified.

Patients must have an ECOG performance status of 0-1.

Patients must be willing to return to NIH for follow-up.

Patients must be able to provide informed consent as demonstrated by the signed consent.

Patients must be 2 or more months from abdominal or thoracic surgery.

No patients with medical contraindication to abdominal exploration.

No patients with recurrent disease detected by conventional imaging studies as outlined above. Metastatic disease localized outside of the abdominal cavity by conventional imaging studies as outlined above. Patients must weigh less than 136 kgs. which is the weight limit for the scanner tables.

No patients with previous injection of murine monoclonal antibodies: Human anti-mouse assay (HAMA) will be performed in patients with prior history of receiving murine monoclonal antibodies.

No patients that are pregnant or breast feeding.

Patients who are HIV + will be excluded.