This study explores the expressive language for children with Down syndrome (DS) through use of augmentative and alternative communication (AAC). Specifically, this study considers the use of speech-generating devices (SGD) (e.g. iPad application) versus the use of manual signing (MS) as communicative modalities of AAC. The purpose of this study was to determine if a child would use words more functionally and/or with greater frequency when taught with SGD or MS, and if he would develop a preference for one method of AAC over the other. With this knowledge base, different methods of AAC can be implemented earlier and help provide young children with DS alternative ways for communication. This could help for more effective communication and increased expressive vocabularies for young children with DS. The study conducted was a single-subject, within-subject, experimental study with a withdrawal design. This study sought to teach five new words in each modality (SGD and MS) to two four-year old males with a diagnosis of DS. The study indicated that each participant was able to acquire some use of both modalities, but had a clear preferred method of communication. The results suggest that children with DS can learn words more functionally or with greater frequency from either method, depending on a variety of factors including personal preference. These results show that SGD and MS are effective methods of AAC for young children with DS.