The extreme brevity of Microblog posts (such as ‘tweets’) exacerbates the well-known vocabulary mismatch problem when retrieving tweets in response to user queries. In this study, we explore various query expansion approaches as a way to address this problem. We use the Web as a source of query expansion terms. We also tried a variation of a standard pseudo-relevance feedback method. Results on the TREC 2011 Microblog test data (TWEETS11 corpus) are very promising – significant improvements are obtained over a baseline retrieval strategy that uses no query expansion. Since many of the TREC queries were oriented towards the news genre, we also tried using only news sites (BBC and NYTIMES) in the hope that these would be a cleaner, less noisy source for expansion terms. This turned out to be counter-productive.