Almost every large library practises intellectual indexing, yet electronic catalogs are still restricted as far as their usability for thematic searches is concerned. Automatic indexing can increase data input into catalogs and improve document retrievability without much additional personnel expenditure. Language analysis technologies suitable for automatic index term creation are available and offer a number of retrieval advantages as compared with common full text indexing. This article focuses on the pros and cons of the two indexation systems MILOS and intelligentCAPTURE.