Eggs have been recognized as a source of biologically active substances, with significant therapeutic potential. Some of these egg components have been the subject of intense study and are currently produced and used onan industrial scale. Research has allowed a thorough understanding of the egg andits components for the manipulation of egg contents, to further enhance their nutritional and therapeutic potential. Feeding of hens special diets to produce eggs with increased levels of certain nutrients and the immunization of hens to produce specific egg yolk immunoglobulins, capable of preventing and treating bacterial and viral infections are in vogue.