The production of therapeutic proteins in transgenic animals started in the 1980s and it is a very popular and widely used technique until today. Mouse, goats and chickens are mostly used as transgenic animals. These animals are kept in isolated farms or laboratories so that disease and infection could be controlled and minimised. The procedure of getting transgenic animals is a very delicate and sensitive process of implanting a desired transgene in the animal's genom, as well as the process of purification of that produced protein. A popular method of protein production (mostly antibodies and enzymes) is by directing it syintheis in the milk or the albumen (egg-white) of the egg of the transgenic animal. In that way large amounts of recombinant protein can be produced including the posttranslational modifications. The purification of the protein is done by many filtration steps and affinity chromatography paralleled with immunologic, microbiological and virus analysis. The final purpose of the produced therapeutic proteins is the use in the clinic. To achieve that, the protein has to pass clinical testing and evaluation. Even today, the production of a protein is an expensive process, which still presents an obstacle for faster development of new candidate proteins. Medication that have reach the market so far (e.g. Atryn, Kanuma) are considered pioneers which will pave the patht for new research and improvement of the field of therapeutic protein production in transgenic animals