In a book prepared by the Head of the Department of Medical Informatics and Statistics of the MMA . and . M. Sechenova, we are talking about the statistical processing of medical data with the help of packages of statistical programs, that is, about probability theory and mathematical statistics for physicians Not only mathematical results and technical methods of data processing are presented, but also some issues of planning statistical research and interpretation of the results obtained. The structure and sequence of the presentation of the material is sharply different from the usual for textbooks on probability theory and mathematical statistics. They, in accordance with internal logic, first set out the theory of probabilities, then on the basis of the apparatus - mathematical statistics, and at the end they discuss practical application issues, in particular the use of software. And in this book, the sequence of presentation of the material corresponds to the sequence of actions in statistical data processing, so the book needs to be mastered in parallel with the processing of actual data. The book consists of two parallel parts. When describing how to enter data and use specific data processing methods, an accurate description is given of how to use the program and what commands need to be executed. When describing how to understand the results obtained, the necessary elements of the theory are given.