Autism spectrum disorder (ASD) is defined as a neurodevelopmental disorder that occurs in the first 3 years of life and manifests itself in persistent deficiencies in social communication and social interaction and limited, repetitive patterns of behavior, interests, and activities (DSM 5, 2013). The new release of the DSM has led to major changes in the definition of autism spectrum disorders. One of these changes is the omission of the language criteria when describing and diagnosing ASD. Although in the past the criteria of language disorder was considered crucial, DSM 5 states that language disorder may or may not occur in addition to ASD. This view has drawn criticism from the American Speech Therapy Society (ASHA), which believes the new DSM overlooks the importance of language disorder criteria for defining ASD, which could lead to misdiagnosis and inadequate therapeutic procedures, as language disorder in both form and content are clinically significant and represent indicators for ASD (ASHA, 2012). Numerous researches, literature as well as experiences from clinical practice confirm that language disorder is an integral part of the picture of ASD. The language skills of people with ASD are diverse. According to research by Lord et al. (2004) 20% of individuals with PSA do not develop functional speech at all, while some individuals do not have very different abilities from individuals with typical language skills. Nevertheless, most children with PSA develop some form of spontaneous language expression, but their language development is atypical. Children with ASD show significant difficulties in language comprehension and language production at the level of all language components. Echolalia, idiosyncratic phrases, inversion of pronouns, and similar features specific to PSA are also common. Despite difficulties in language development, children with PSA can make significant progress in language skills through early involvement in science-based intervention procedures. Since the successful promotion of language development of children with PSA is a great challenge for professionals and families of children with PSA, the aim of this thesis was to give an overview of current knowledge in the field of promoting language development of children with ASD and present those intervention methods and techniques which were proved successful. The guidelines given in this thesis are based on scientifically based methods and are practical and applicable both in the clinical work of speech and language therapists and for parents at home.