Foodborne diseases, i.e. illnesses due to contaminated food, are one of the most widespread problems of the contemporary world. They are toxic or infectious by nature and are caused by agents which enter the body through the ingestion of contaminated food or water. These agents can be chemical like pesticide residues and toxic metals or biological like pathogenic microorganisms. Foods contaminated by biological agents are, however, the major cause of foodborne disease. Data recorded in different countries show that the incidence of some of these diseases has increased dramatically over the past few years, but because of under-reporting the data are of limited value and cannot be compared between countries. In most countries, individual cases of illness are usually not reported. A sentinel surveillance system, started as a pilot study in the Netherlands, was shown to be feasible for the registration of some foodborne infections. Based on this study, it can be estimated that each year Salmonella and Campylobacter cause respectively about 12,000 and 25,000 cases of acute enteritis per million. Case-control studies clearly implicate poultry products as an important source of acute enteritis. New developments in food production and changing trends in food consumption lead to the emergence of new hazards. Additionally, because the population is aging and there has been an increase in the number of individuals with underlying diseases, the state of public health is deteriorating. Campylobacter, Salmonella enteritidis and enterohemorrhagic Escherichia coli are examples of microorganisms that have the opportunity to increase as a consequence of intensive husbandry. Listeria monocytogenes is an example of an organism that causes disease in immunosuppressed individuals.