Purpose to present and to discuss the use of augmentative and alternative communication as a therapeutic tool with the morphosyntax with adolescents with Down syndrome. Methods this pilot study monitored during 12 months four adolescents chronologically aged between 13 and 15 years and mentally aged between 5 and 6 years. It were analyzed the initial and the final assessments, situations of free interaction between the participant and the caregiver videotaped during 30 minutes. The speech samples were analyzed as MLU values considering morphemes and words, comparing both the two situations. All of the participants were submitted to the same procedures during the therapeutic interventions. Picture Communication Symbols (PCS) has been used and the symbols were organized according to a simple syntactic structure (substantive + verb + complement) with a gradual extension, and the elements were rated at the following order: articles, prepositions, pronouns (personals, possessives and demonstratives), and conjunctions. Each therapeutic session was recorded in specific protocol. It was used the Wilcoxon test and the p value considered was 5%. Results spites there were no statistical significant differences, increase in number of morphemes and words used between the both assessments was observed. This improve was represented by the worked elements, including prepositions and conjunctions beyond substantives and verbs. For personal pronouns there was tendency to significance (p=0,068). Conclusion the communication system showed to be a therapeutic tool to improve the use of syntactic elements in statement structures, as articles, prepositions and conjunctions, which use for individuals with Down syndrome are difficult.