This study describes the principles of group technology, and attempts to provide an introduction to the methodology and benefits of the subject. It also indicates the current scale of development by reference to industrial applications. Some emphasis has been placed on the reorganization of manufacturing facilities for ordered work flow, with easier and better control, to yield the greatest benefits. The text also includes descriptions of actual applications of the basic approach to design, estimating and planning. Each application of group technology is different, and hence the text is devoted to principles, practical advice regarding specific techniques, and examples from existing practice. The implementation of group technology can fundamentally affect the overall structure and pattern of the working day for most employees and involve them in a new way of thinking. The long-term effects are therefore of considerable importance. The justification for technological or structural change must be seen in terms of the economic and organizational benefits that result. The sociological and organizational implications rank with equal importance to the technological developments. These implications are discussed in general terms and by means of applications from the USA, Europe and Japan.