Translating idioms is one of the most difficult tasks for human translators and translation machines alike. The main problems consist in recognizing an idiom and in distinguishing idiomatic from non-idiomatic usage. Recognition is difficult since many idioms can be modified and others can be discontinuously spread over a clause. But with the help of systematic idiom collections and special rules the recognition of an idiom candidate is always possible. The distinction between idiomatic and non-idiomatic usage is more problematic. Sometimes this can be done by means of special words that are only used in an idiom. But in general this distinction is a question of semantics and pragmatics and therefore beyond the abilities of current translation systems. In this paper we investigate the requirements for automatically recognizing idioms and we check whether idiom recognition is possible within current translation systems, i.e. machine translation and translation memory systems. This is of current interest since the developers of translation systems have started to include huge idiom collections in their products.