Monoclonal antibody SM 92 is involved in the immunophenotype of gastrointestinal and liver cells, SM 43 in ovarian cells, and SM 13 in lung cells. Based on a study of 61 breast adenocarcinoma patients, we found that tumors reacting with SM 92 appear associated with liver metastases, SM 43 with ovarian metastases, and SM 13 with lung metastases. These associations are highly significant. They lend some support to the concept that tumor cells that metastasize tend to go to sites where cells normally have the same surface antigens.