Objective: This study compares the effect of speech therapy and picture exchange communication system (PECS) on communication development of 4-8 year old autistic children.

Materials & Methods: This is an experimental and comparison study. In this study 10 subjects including PECS and speech therapy groups were selected using the available sampling method on the base of including and excluding criteria. Both groups were matched according to age and developmental indices of Niusha scale. Dependent variables were listening, receptive language, expressive language, cognition, speech and social communication. Intervention was applied for both groups similarly divided in 40 minute sessions 3 times a weak for 3 months. Our parameters were evaluated by Niusha development scale before and after interventions. The results were analyzed clinically and statistically by sum-ranks willkokson and rank- signed willkokson.

Results: Post test comparison between the two groups revealed that the members of PECS group had a more progress in listening, receptive language, cognition and social communication skills rather than speech therapy group. But these differences were not significant statistically and T(sum ranks) was between critical values.

Conclusion: considering the results, it could be concluded that PECS is a effective strategy to train non-verbal autistic children. Moreover it could be used as a supplement teaching method beside other therapeutic method such as speech therapy.