Catalan lexicography has traditionally dealt with idioms either as alphabetically ordered lemmas or as non-lemmatic stems. In the case of a non-lemmatic approach, idioms are registered using either the first word with semantic content or the word considered to reflect the main semantic content of the expression. This paper shows that both traditional semasiologic and onomasiologic approaches to the description of idioms have been unified in a new conceptual dictionary of Catalan idioms. This dictionary introduces detailed grammatical, linguistic, and conceptual information for each idiomatic expression. In addition, a CD-ROM is provided, which allows any search combination using the query boxes of the dictionary's data base previously built up. The present paper describes the innovations this dictionary presents, and focuses on the selection of concepts, the specification of cross-referential conceptual relationships among idiomatic expressions, and the advantages it has over other dictionaries in teaching and learning idioms. © 2005 Oxford University Press. All rights reserved.