This book constitutes the thoroughly refereed proceedings of the 10th Workshop of the Cross Language Evaluation Forum, CLEF 2010, held in Corfu, Greece, in September/October 2009.The volume reports experiments on various types of textual document collections. It is divided into six main sections presenting the results of the following tracks: Multilingual Document Retrieval (Ad-Hoc), Multiple Language Question Answering (QA@CLEF), Multilingual Information Filtering (INFILE@CLEF), Intellectual Property (CLEF-IP) and Log File Analysis (LogCLEF), plus the activities of the MorphoChallenge Program.