The work presents the results of a comprehensive and in-depth theoretical and empirical study of issues of qualification of theft of another's property and assignment of punishment by the courts for their commission, taking into account the size of the material damage caused by these crimes. The book presents the results of the research of statistic data on acquisitive crimes, materials of criminal cases of thefts which were examined by the courts of the Russian Federation and also the monographic literature; the results of surveys of the population and law enforcement bodies' employees conducted by the author are presented; the factors which influence the correct qualification of the crimes and the size of the punishment imposed by the courts are distinguished. The authors also present a new mathematical methodology of sentencing for this category of crimes which takes into account the amount of damage done, the number of criminal episodes, the number of mitigating and aggravating circumstances in court proceedings. The book is recommended for legal researchers, legal practitioners and students of criminal law disciplines.