CD molecules are cell-surface antigens identifiable by their reactions with specific monoclonal antibodies, which represent an important system for identifying and differentiating human cells. The CD Antigen Information Finder was adapted from Current Protocols in Immunology (Beare, et al., 2008. Monoclonal Antibodies to Human Cell Surface Antigens. Curr. Protoc. Immunology. 80:A.4A.1–A.4A.73) and includes data on the molecular weight, family, molecular structure, cellular expression patterns, function, and biomedical usefulness of the molecule. The database is searchable by the official CD designation of the antigen as well as by synonyms and other keywords including associated diseases and tissue/organ names.