Objective Communication deficiency is one of the diagnostic criteria for autism, which leads to difficulty in learning speech and linguistic skills. Nowadays, it is common to use play therapy for supporting children with autism. Play therapy is an active approach that helps a child to reveal his conscious and unconscious feelings through playing. The present study aimed to determine the effectiveness of group play therapy on the communication skills of children with high functioning autism.
Materials & Methods The present research was an experimental study, including a pretest and posttest design with a control group. Twelve 5-8 years old boys with high functioning autism were selected purposively from the Autism Charity Foundation in Tehran in 2013. All subjects were included according to get a diagnose of high functioning autism, literacy of parents to complete the questionnaire, lack of sensory disorders such as visual or auditory disorders, lack of physical or motor disorders such as cerebral palsy, not attending to the same play therapy intervention program simultaneously. All subjects were assigned randomly to the experimental and control groups (6 children in each group). The experimental group participated in 20 sessions (three times a week; 45 to 60 minutes for each session) and received group play therapy along with the routine program (mental and physical occupational therapy, and speech therapy). However, the control group received only the routine program. The communication skills of all the children were evaluated using the Gilliam Autism Rating Scale (GARS) before, at 20th session, and 2 months after the intervention. The collected data from two situations (pre-test, post-test) were analyzed by analysis of covariance. Repeated measure test was used to determine the lasting effect of group play therapy on the communication of boys after two months follow-up.
Results The findings of the analysis of covariance showed that the group play therapy significantly influenced the communication of male children with high functioning autism. In addition, it was found that the effects of the group play therapy lasted significantly on the communication skills of the children even at two months follow-up (P<0.001). 
Conclusion It is concluded that the group play therapy can help the children to understand and communicate well. This therapy can be used as a complementary training and therapeutic method for children with high functioning autism to help improve their communication deficiencies.