We introduce a statistical model for abbreviation disambiguation in Web search, based on analysis of Web data resources, including anchor text, click log and query log. By combining evidence from multiple sources, we are able to accurately disambiguate the abbreviation in queries. Experiments on real Web search queries show promising results. Categories and Subject Descriptors H.3.3 [Information Systems]: Information Storage and Retrieval--Query formulation General Terms Algorithms, Experimentation Keywords Web search, Query expansion, Text association, Abbreviation