The monograph provides an overview of current data on the distribution and features of manifestation of lateral functions (asymmetry of use) of extremities in vertebrates and, in particular, in mammals. The monograph focuses on a detailed description of the lateralized functions of the forelimb in quadrupedal and bipedal marsupial mammals studied in captivity and in nature. The emphasis is given to natural manifestations of lateralization in the daily activity of animals. A comparison of lateralization in bipedal and quadrupedal species, as well as a study of lateralization in bimanual manipulations, was previously performed only among primates. The infl uence of the position of the animal's body on the manifestation of asymmetric use of the forelimb is demonstrated for mammals not belonging to the Primates order. During two expeditions to Australia, the authors obtained data on motor lateralization in the marsupials in nature. This allowed comparing directly the data on the preferences of one limb in animals of the same species in nature and in captivity in identical types of behavior for the fi rst time. The infl uence of various factors (complexity and nature of the performed action, sex, age) on the direction and force of lateralization in different species of marsupials was assessed. The lateralization of functions of the forelimb is compared in marsupials and placental mammals. The evolutionary aspects of the development of the expressed handedness in bipedal species, including humans, are considered. The book can be of interest to zoologists, physiologists, evolutionary biologists, specialists in the fi eld of brain asymmetry and human evolution, teachers and students of the biological faculties of universities, as well as all those interested in the evolution of man and mammals. Figures 34, Tables 21, Bibliography 275.