"Houghton Mifflin: Invitations to Literacy," developed by the Houghton Mifflin Company, is an integrated K-8 reading and language arts program. The philosophy behind the program is that literacy instruction should stimulate, teach, and extend the communication and thinking skills that will allow students to become effective readers, writers, communicators, and lifelong learners. The program is structured around themes. It includes hands-on activities that allow students to collaborate or share information on a theme-related project with other classrooms around the world and virtual field trips to Internet sites that have content, activities, and projects related to the theme. The What Works Clearinghouse (WWC) identified 4 studies of Houghton Mifflin: Invitations to Literacy that were published or released between 1983 and 2008. No studies of "Houghton Mifflin: Invitations to Literacy" that fall within the scope of the Beginning Reading protocol meet WWC evidence standards. The lack of studies meeting WWC evidence standards means that, at this time, the WWC is unable to draw any conclusions based on research about the effectiveness or ineffectiveness of the program. [This review refers to studies of "Houghton Mifflin: Invitations to Literacy" in grades K-3.]