The heart of language development is vocabulary learning. Although acquisition centers on learning individual words and their meanings, it extends beyond this (Nagy & Scott, 2000). As words are learned, they become embedded in a net- work of semantic connections to other words (Landauer & Dumais, 1997). Not only verbal definitions and interconnections but also visual images contribute to the representations of words in memory (Sadoski, 2005). The correlation between students’ vocabulary knowledge and their reading comprehension is extremely high and positive (rs ranging from .63 to .73), almost as high as the correlation between different measures of reading comprehension (rs ranging from .64 to .79; Cutting & Scarborough, 2006). The heavy involvement of vo- cabulary in reading ability underscores its importance for academic achievement in school. Thus, it is essential to advance our understanding about how students’ vocabularies grow and how instruction can support this growth.The purpose of this viewpoint article is to consider theory and evidence supporting the contribution and importance of word spellings for vocabulary learning and instruction. First, we review background studies revealing how written words are stored in memory and how they influence speech. This research has revealed that spellings exert a powerful influence, so it is surprising that the contribution of orthography to vocabulary learning has been neglected by vocabulary researchers. Next we present evidence for the effect of written words on vocabulary learning by summarizing the results of two experiments. Finally we discuss the implications of this work for theory and practice.