A phase I and II clinical trial with indium-111-labeled anticarcinoembryonic-antigen monoclonal antibody ZCE-025 (In-111 ZCE-025) was initiated. Fifteen patients with colorectal tumors underwent external scintigraphy following the administration of 5.5 mCi (203.5 MBq) In-111 ZCE-025 at doses of 2.5-80.0 mg. Eighteen of 20 documented tumor sites, excluding those in the liver, were detected with In-111 ZCE-025. Lesions less than 1.5 cm could not be detected. Twenty-five percent of liver metastases exhibited positive accumulation of In-111 ZCE-025 at doses of 40-80 mg. No side effects were encountered. Because of the high detection rate of lymph node metastases from colorectal carcinoma with In-111 ZCE-025, this technique may be helpful in preoperative staging of patients with colorectal tumors, as well as in distinguishing recurrent tumors from postoperative or postradiation changes seen on computed tomography scans or other radiologic images.