The Kabat antibody sequence database has for many years been the primary site for depositing sequence information on antibodies and other proteins of immunological interest. The chief drawback of this database has been that it has only been available in the form of a printed book (Kabat et al., Sequences of Proteins of Immunological Interest, 1991). These data have recently become available on the global computer Internet, but no method of searching the data has, as yet, been provided. Here, the development of a specialized database program for accessing the antibody data is described. This database software has been made accessible over the World Wide Web, together with a program which allows a novel antibody sequence to be tested against the Kabat sequence database, to identify unusual features of an antibody sequence which may represent cloning artifacts or sequencing errors.