Development of the methods of molecular and cellular biology now allows specific genetic manipulations of laboratory animals leading to the introduction of an exogenous gene to their genome or elimination of a particular endogenous gene. This approach represents an invaluable biological tool for a better understanding of basic physiological and pathological processes. In all fields of biomedical research, transgenic and knockout animals have contributed greatly to understanding the molecular cause of several human diseases and allowed production of their animal models, which represent a useful tool for development of new medical drugs and therapeutic procedures for the treatment of human diseases. The aim of this short review is to provide a brief survey of the production of genetically modified animal and to discus their importance human medicine. Fig. 2, Ref. 19.)