Interactions between users and information access systems can be analyzed and studied to gather user preferences and to learn what a user likes the most, and to use this information to adapt the search to users and personalize the presentation of results. The LogCLEF lab - ”A benchmarking activity on Multilingual Log File Analysis: Language identification, query classification, success of a query” deals with information contained in query logs of search engines and digital libraries from which knowledge can be mined to understand search behavior in multilingual context. LogCLEF has created the first long-term standard collection for evaluation purposes in the area of log analysis. The LogCLEF 2011 lab is the continuation of the past two editions: as a pilot task in CLEF 2009, and a workshop in CLEF 2010. The Cross-Language Evaluation Forum (CLEF) promotes research and development in multilingual information access and is an activity of the PROMISE Network of Excellence.