This thesis presents a best-practice model for term planning for a language, based on the literature and on three qualitative case studies: TERMCAT (the term planning organisation for Catalan), Terminologicentrum TNC (the term planning organisation for Swedish) and the Irish-language term planning organisations, principally the Terminology Committee (Foras na Gaeilge) and Fiontar, DCU. Although the literature on the subject is underdeveloped, and a complete model cannot be derived from it, a basic structure for term planning is constructed, consisting of eight stages: preparation/planning, research, standardisation, dissemination, implantation, evaluation, modernisation/maintenance and training. This structure forms the basis of the case study research. A new, comprehensive model for term planning is then developed and described, combining elements from each of the three cases and from the literature. The model developed is not limited to any one particular situation of term planning for a language, and is therefore both general and adaptable. Because it is the first of its kind, this study is of an exploratory nature; it suggests success factors for term planning and explores the limits of the literature-based model. Gaps in the literature and limits to the socioterminological approach to term planning are identified and recommendations for further research made.