Autism spectrum disorders (ASD) are commonly occurring group of neurodevelopmental conditions and applied behaviour analysis (ABA) is used to treat a range of their core symptoms as well as psychopathology and challenging behaviours. Present study is a systematic analysis that synthesizes present literature about use and efficacy of ABA to treat ASD, trends in use of ABA, and variables that may affect the treatment. For these 18 studies were selected and analysed it is extracted that as an early childhood intervention ABA is effective treatment of ASD. Systematic review shows that efficacy remains unquestionable even if it is implemented in some later stage of childhood. It is also suggested that ABA improves social, cognitive, language, adaptive and independent living skills as well as functional, cognitive domain and developmental delays. Parental training, professional education, and individual factors impact efficacy of ABA, however, conclusions regarding intervention's intensity and duration on efficacy of intervention need further research