This paper presents an original natural language processing (NLP) approach for building of back-of-the-book indexes. The indexing system proposed, IndDoc, exploits some terminological tools and automatically builds an index draft of the analysis of the document text. The indexer then has to validate that index draft through a dedicated interface. This approach has been tested on several documents with promising results. Relying on their experience in developing and testing the IndDoc indexing system, the authors aim at assessing the contribution of terminological analysis as well as the level of maturity that computational terminology has reached in the indexing perspective.