The aim of this research was to describe the language intervention process of two brothers with pervasive developmental disorders, through a longitudinal clinical case study. Two brothers - one nine and the other 11 years old - participated in the study. Subjects had diagnosis of autism (Case 1) and pervasive developmental disorder-not otherwise specified (Case 2), respectively. As a procedure for data collection and analysis, a longitudinal study was carried out through a follow up of the cases during the four years of language therapy. The procedure included filmed therapy sessions, documental analysis of information contained in the patients' records regarding anamnesis, assessments and therapeutic reports, and multidisciplinary evaluations and exams. In both cases there was an improvement on visual contact, social interaction, vocabulary and symbolic play. For Case 1, there was an increase from 2.0 to 6.2 communicative acts per minute; for Case 2, an increase from 3.5 to 8.0 acts. Both subjects demonstrated predominance of the verbal communicative mean and greater variety of communicative functions. Other factors influenced these results, such as the intellectual deficiency, the family dynamics, the conflicts on the relationship between the brothers and the school environment in which they were placed. The study confirmed the relevance of the speech-language pathologist in interventions of pervasive developmental disorders, along with multidisciplinary teams, for the discussion of diagnoses and of the most appropriate procedures. Longitudinal studies can contribute for more detailed and reliable analysis of therapeutic intervention in these cases, in order to clarify gaps existent in literature and to support the role of clinical speech-language pathologists.