This book aims to present R program and its capabilities in ratemaking and loss reserving in property and casualty insurance. Generalized Linear Model is a popular statistical tool now used by insurance companies. The model is most often applied in risk assessment for short-term insurance schemes generating mass risk portfolios and in loss reserve prediction. In the book the Authors wish to show the model theoretical fundamentals with respect to a specific function of program R on the one hand, and to present the function application in ratemaking and loss reserving on the other. Each chapter of the book consists of the following parts: theoretical introduction to ratemaking and loss reserving, theoretical introduction and R function in general statistical models, models and empirical examples in R. The book supplements the knowledge gained in courses concerning Non-Life Insurance: Statistical Techniques. It is addressed to students as well as practitioners working in different departments of an insurance company.