Infants’ learning of phonotactic information has great potential to affect language acquisition, particularly vocabulary development. One possible point of influence is on the process of detecting individual words within the fluent stream of speech. Phonotactic patterns provide cues to word boundaries. For example, phonotactic patterns can aid in word segmentation when English speakers hear a phrase such as ‘‘give to” (/gIv tu/) because phonotactic constraints indicate that the sequence /vt/ does not tend to occur within words. Accordingly, phonotactic patterns suggest that the appropri- ate parsing is (/gIv tu/) rather than /gIvt u/ or /gI vtu/. reported that infants can make use of such segmentation cues .They presented 9-month-olds with target nonce words embedded in phrases with phonotactic cues for seg- mentation. That is, the phoneme combinations surrounding the target word’s onset and offset formed phoneme combinations that frequently occur across word boundaries but not within native language (English) words. Infants displayed evidence of segmenting and recognizing the novel words when good phonotactic cues were present but not when they were absent. This work demonstrates that well before infants amass large vocabularies, their early learning about sound combinations has potential to shape lexical development and contribute to the development of the protolexicon.