Purpose: The authors asked whether adolescents with Down syndrome (DS) could fast-map novel nouns and verbs when word learning depended on using the speaker's pragmatic or syntactic cues. Compared with typically developing (TD) comparison children, the authors predicted that syntactic cues would prove harder for the group with DS to use and that action verbs would be harder to fast-map than nouns. Method: Twenty participants with DS, aged 12-18 years, and 19 TD participants, aged 3-6 years, were matched on syntax comprehension and engaged in 4 fast-mapping tasks. Both comprehension and production of novel words were assessed for each task. Through use of hierarchical regression models, hearing, cognition, and working memory were considered as predictors of total comprehension and production performance for each group. Results: Both groups used speaker intent in fast-mapping labels to object referents but performed more poorly on fast-mapping verbs. Neither group appeared to use grammatical cues to disambiguate the intended referent. Syntax comprehension was replicated as a predictor of fast-mapping comprehension for the DS group. Syntax comprehension and chronological age were replicated as predictors of TD fast-mapping. Conclusion: Participants with DS had better recall for the object or action seen most recently during speaker intent tasks. They had better recall for the object presented first and the action presented last during grammatical cue tasks. Response patterns may have depended on the structure of specific task paradigms. Verb acquisition may be facilitated when either the action or label is familiar.