This book is written to discuss the critical issues in selecting conventional and mechanized tunneling methods and lessons learned from the past. The book covers the following main topics: geological and geotechnical parameters affecting tunneling methods, summarizing conventional tunneling and mechanized tunneling methods, the factors affecting the choice of tunneling methods such as the cost of the initial investment, the length of the tunnel, project scheduling, time for mobilization, emerging new technologies. Some examples of changing the tunneling method from conventional to mechanized tunneling or vice versa during the same ongoing project and hybrid tunneling methods in the same project are also given. The book is unique in the subject, aiming at civil, geology, and mining engineering graduate and undergraduate students, researchers, and those dealing with the tunneling business.