An accumulation of research indicates that many words are learned incidentally through the independent reading of text, through oral language discussions, and through reading aloud to children (Elley, 1989; Nagy, Anderson, & Herman, 1987; Penno, Wilkinson, & Moore, 2002). Even a single incidental encounter with a word in text can facilitate word learning (Nagy et al., 1987; Schwanenflugel, Stahl, & McFalls, 1997; Swanborn & de Glopper, 1999). However, there is also evidence that children are exposed differentially to infrequent words both in independent reading and in their homes (Hart & Risley, 1995; Stanovich, 1986). Furthermore, recognition is increasing of the importance of informational literacy and students’ knowledge of academic language (Duke, 2000; Hirsch, 2003). Every content area has a set of specific concepts and vocabulary. The National Reading Panel Report (NICHD, 2000) calls for an increased focus on vocabulary derived from content area materials. Yet, there appears to be little consensus on how vocabulary should be presented in informational texts and little regard given to factors that might facilitate students’ word learning from such texts (Myerson, Ford, Jones, & Ward, 1991).