We compared immunization data in the Defense Medical Surveillance System (DMSS) and immunization data for service members with an anthrax vaccine-associated adverse event reported to the Vaccine Adverse Event Reporting System (VAERS) during January 1998 through December 2004. Our main measure of agreement was sensitivity of the DMSS conditional on an immunization record(s) occurring in VAERS. The sensitivity of DMSS was 73% for all vaccines and 74% for the anthrax vaccine on the VAERS index immunization date. Our study is the first to quantify the agreement between immunization records in VAERS and DMSS. Our data suggest the immunization information in military VAERS reports and the DMSS is similar for anthrax and non-anthrax immunizations.