Cancer-related Immunological Gene Database (CIG-DB) is the database for human or mouse immunoglobulin and T cell receptor genes investigated in cancer studies. This database is designed as a sequence- and reference-based platform to explore public Ig/TCR/epitope sequences so that the information can be utilized for the advanced cancer clinical studies (e.g. genetic engineering of Ig/TCR in immunotherapy, design of epitope peptides as cancer vaccines). Users can therefore perform two ways of searches: (i) by sequences (V-regions, J-regions, and CDR3) or (ii) by references (titles, abstracts, MeSH terms, etc.). Moreover, the CIG-DB is equipped with sequence analysis tools based on BLAST and CLUSTALW, which enables comparison between cancer-related Ig/TCR/epitope sequences and non-related ones, or between in-house sequence data from patients and all data in the database.