The introduction of chain saws and tractors in the early 1950's marked the beginning of a change in tree harvesting techniques from the old manual methods to mechanized operations. It was followed by a rapid evolution both technically and systematically. Hence, the requirements for improved know­ ledge of operational efficiency also increased. Changing relations between Man, machines and environment brought about new experiences and awareness of a physiological and ergonomic nature. Improved knowledge of both machine technology and planning of work on a small or large scale has grown increa­ singly important for an efficient utilization of expensive machines and other equipment. The need for a textbook on tree harvesting techniques including expe­ riences made in recent years is enhanced. The book presented here is prima­ rily based on lectures given on the subject of Forest Techniques at the Faculty of Forestry at the Swedish University of Agricultural Sciences and after modifications also at the University of Nairobi (Kenya). Thus, the book is written primarily for students at the faculties and institutes of forestry. However, it is also useful for persons actively occupied in forest operations. The presentation of this book in its original Swedish version in 1972 created a considerable interest in the preparation of a condensed edition in English. Thus interest has been expressed in Finland, Norway, Holland, Canada, U.S.A., Brazil, Japan, Poland, Scotland and Yugoslavia.