BACKGROUND: Augmentative and alternative communication (AAC)1 systems are commonly used to support children with complex communication needs in Australian preschools. However, such systems will only be effective if they contain words and messages that adequately meet these children's communication needs. The aim of this study was to identify the words most frequently and commonly used by typically developing Australian preschool-aged children, in order to inform the selection of vocabulary for their classmates who use AAC. METHOD: Communication samples were collected from 6 typically developing children during regular preschool activities. The samples were analysed to determine the number of different words used by the children, the frequency with which each word was used, and the commonality of use across children. RESULTS: The children used a small core vocabulary comprising frequently and commonly used words, together with large and highly individualised fringe vocabularies. CONCLUSIONS: The results are consistent with the findings of previous studies, and highlight the importance of providing both core and fringe vocabulary to preschool-aged children who use AAC.