BACKGROUND: the linguistic evolution of a subject with unknown syndrome, characterized by motor impairment and absence of speech after the introduction of Augmentative and Alternative Communication (AAC) board. PROCEDURES: we performed a case study of a subject that was 6 years and 8 months old at the beginning of the study. The study period was from August 2007 to December 2008. The subject had already been undergoing speech-language therapy since 2002, with complaint of saliva flow and absence of speech. He had little phonoaudiological progress in terms of orality. During the study period, the subject was given speech-language intervention through introduction of AAC in a dialogic functioning that involved his family and school. Observational assessments were performed using the PROC before and after the study period. RESULTS: the subject's progress was positive in relation to understanding and linguistic expression. Use of AAC favored manifestation of speech. Both within the family and at school there was good incorporation of such resource, considering the theoretical perspective in which it was introduced. CONCLUSION: AAC, in a dialogic perspective, had good generalization of use, which enabled linguistic progresses in this case.