Assessed long-term predictive validity of the MacArthur Communicative Development Inventories: Words and Sentences (CDI:WS) for children's expressive and receptive vocabulary development. Sixty-one New Zealand children were assessed with a New Zealand version of the CDI, and with the Expressive Vocabulary Test and Peabody Picture Vocabulary Test-III. Excellent reliability and predictive validity of the New Zealand CDI:WS was obtained. (Author/VWL)