This paper describes the work done in the TIPS project about the construction of a thesaurus. This construction is a merge from a compilation of data from several web sources. These data comes from manual work, some data are real thesaurus, other are indexing recommendations. The merge is done with automatically extracted terms from large text corpora. The automatic extraction is based on both syntax and statistics. We present in this paper the way thesaurus are built and the results on Scientific corpus in the context of the TIPS project. This short paper emphasis on some technical aspects.