Normative data on vocabulary size of Italian children with Down syndrome are
not available at the present time. The principal aim of this study is to assess word production
and its relationships with chronological and developmental age in this population, using Il Primo Vocabolario del Bambino (Caselli and Casadio, 1995) (i.e., the Italian version of the MacArthur-Bates Communicative Development Inventories) whose validity in this population has been already demonstrated. An amount of 152 questionnaires has been collected from parents of children with Down syndrome aged two to five years. Word production appears to be correlated to developmental age but not to chronological age. Moreover, in comparison with typically developing children, lexical development seems to lag behind their cognitive development.