Museums are competing with a vast variety of Internet-based information delivery sites to keep the public interested in their institutions. To keep pace Museums are increasingly turning to the use of Web 2.0 tools to draw in the public and maintain a standing as cultural and educational leaders. Several museums have started using Twitter. This research paper explores the different ways that the Hirshhorn Museum and Sculpture Garden and the Smithsonian National Air and Space Museum use Twitter to develop and engage audiences. In this six-month qualitative study, tweets used for audience development and engagement were codified. Analyzing Twitter data suggests that the two institutions use Twitter in a consistent manner concentrating on: linking resources, creatively engaging the public to utilize new social media tools, and attempting to create an active two-way form of communication. As social media becomes more pervasive and museums adopt it for audience development and engagement, careful understanding of the advantages and disadvantages of this media need to be considered. (Contains 4 figures.)