Genetically modified food and feed crops have entered the Western market, and genetically modified animals may follow in the near future. The issues that are commonly addressed in the assessment of the safety of genetically modified crops are discussed, as well as the analogous issues that may arise for genetically modified animals. For safety assessment, the degree of substantial equivalence of the novel food- or feed-organism to an appropriate counterpart should be established. Based upon the differences thus found, a further strategy for the safety assessment is chosen. This may, for example, take the testing of a novel food or feed for its potential toxicity and allergenicity. Another issue is that of the possible transfer of genes from the genetically modified organism to others. This would be a concern, for example, if the introduced DNA comprised genes coding for resistance against clinically important antibiotics. Unanticipated long term health effects of the genetically modified food or feed can be monitored by postmarket surveillance. National regulations for food and feed derived from genetically modified organisms may differ, but they are based upon the same underlying principles. The regulatory status of genetically modified animals may differ from that of genetically modified crops, as the foreign gene in some animals will be regarded a veterinary medicine. National regulatory experience with transgenic food animals has been gained in a few cases so far. The FAO/WHO has initiated the harmonization of the food safety evaluation of genetically modified organisms.