Listeria monocytogenes, a psychrotrophic organism capable of growing at refrigeration temperatures, is of major concern in extended shelf life, refrigerated foods. Considering that as much as 80-90% of human listeriosis cases are linked to the ingestion of contaminated food, human cases are predominantly seen in high-risk individuals, including organ-transplant recipients, patients with AIDS and HIV-infected individuals, pregnant women, cancer patients, and the elderly. In 2001, the Canadian Listeriosis Reference Service (LRS) was created by the Bureau of Microbial Hazards (Health Canada) and the National Microbiology Laboratory (now part of the Public Health Agency of Canada). Major goals of the LRS include investigation of listeriosis cases and maintenance of a national collection of isolates. The LRS intends to create a comprehensive molecular epidemiological database of all isolates in Canada for use as a resource for outbreak investigations, research and other microbiological investigations. The PFGE profiles are being established and stored for clinical, food, environmental, and possibly animal strains of L. monocytogenes. The LRS pursues research activities for investigation and implementation of other molecular methods for characterizing L. monocytogenes isolates. Ribotyping, Multi-locus Sequence Typing (MLST), Variable Number of Tandem Repeats (VNTR), Multi-locus virulence sequence typing (MLVA), microarray- based technologies and sequence-based typing schemes, are being investigated on selected diversity sets. The LRS has also used PFGE typing for outbreak investigations. The molecular epidemiological data, timely coordination and exchange of information should help to reduce the incidence of listeriosis in Canada. In Canada, listeriosis is not a national notifiable disease, except for the province of Quebec, where it has been since 1999. The LRS, Canadian Public Health Laboratory Network, and federal epidemiologists are currently working on making human listeriosis notifiable throughout Canada.