Recently it was found that immunoanalysis of carcinoembryonic antigen (CEA) levels in gallbladder bile may be a sensitive method to detect colorectal liver metastases in humans. Methods used in the past for the detection of CEA in various body fluids were cumbersome and time consuming, requiring acid extraction, extensive dialysis, and column purification. Single-step, solid-phase radioimmunoassays, designed specifically for serum CEA analysis, were developed commercially to replace these methods. Parameters and methodology necessary to adapt these kits for use with gallbladder bile are presented here. A combination of pretreatment procedures for bile, before radioimmunoassay, permit rapid, reproducible, and accurate measurement of CEA levels in gallbladder bile.