The delayed cutaneous hypersensitivity reaction to carcinoembryonic antigen (CEA) was tested in 84 patients with different diseases including large bowel adenocarcinoma and breast carcinoma, with or without metastasis, liver cirrhosis and inflammatory or degenerative diseases. Positive skin test to CEA was observed in a small proportion (11%) of the patients tested. No difference in positive skin test reactions was observed in the 6 different groups of patients. Similar delayed cutaneous hypersensitivity reactions were found to various amount of CEA ranging from 0.5 to 25 micrograms. No correlation was seen between the results of skin test and blood CEA levels.