AbstractCross-language retrieval systems use queries in one natural language to guide retrieval of documents that might be written in another. Acquisition and representation of translation knowledge plays a central role in this process. This paper explores the utility of two sources of translation knowledge for cross-language retrieval. We have implemented six query translation techniques that use bilingual term lists and one based on direct use of the translation output from an existing machine translation system; these are compared with a document translation technique that uses output from the same machine translation system. Average precision measures on a TREC collection suggest that arbitrarily selecting a single dictionary translation is typically no less effective than using every translation in the dictionary, that query translation using a machine translation system can achieve somewhat better effectiveness than simpler techniques, and that document translation may result in further improvements in retrieval effectiveness under some conditions.