As part of the writing of the Sanasilva report 1997 on forest condition in Switzerland, an attempt was made to clarify and harmonise the German → terminology on forest condition. A small team of forest scientists, assisted by a → terminologist, collaborated in a terminological project. They adopted the following procedure: 1) → definition of aims and coverage of our → terminology; 2) collection of → terms from the technical literature and development of a terminological database; 3) assessment of type (technical/non-technical → term) and status according to our purpose (recommended → term, recommended → synonym, recommended → quasi-synonym, non-recommended → term); and 4) → definition of → terms. Recommended → terms, → synonyms and → quasi-synonyms had to be in common use, short, as self-explanatory as possible, and constructed consistently throughout this → terminology. → Definitions had to be short, precise, and widely accepted in our field of study. Altogether 251 related German → terms were collected, and 156 of them were defined. The → terminology developed in this project provided a useful framework for the Sanasilva report 1997, and allowed many basic issues related to forest condition to be clarified before the contributions to the report were written. The authors encourage readers to undertake similar projects and provide a list of recommendations.