This book presents the potential of the Monte Carlo (MC) technique to solve mathematical and physical problems of great complexity. This book focusses on the study of the electron-solid interaction (transport MC) and presents some physical problems related to the transport of hot electrons in solid targets using transport MC. The numerical and theoretical results are validated through a comparison with experimental results. The author also addresses methodological aspects. In particular, systematic comparisons among different calculation schemes are presented. Different expressions for the calculation of cross sections and/or stopping power and different simulation methods are described and discussed.