دAbstract                                                                                  

Objective: The purpose of present study was to compare Applied Behavior Analysis (ABA), Pivotal Response Treatment (PRT), and the integrated (ABA and PRT) method on the vocabulary span of children with autism spectrom disorder. Method:  Using  multistage  random  sampling method, thirty children aged four to six (13 girls and 17 boys) were selected from two autism training centers in tehran. The subjects were  randomly divided in three Integrated, ABA, and PRT treatment  groups. Research method was semi-experimental  with  expanded  pre-test, post-test  group design. To screen the subjects, Giliam Autism Rating Scale (GARS) and a vocabulary assessment checklist were used. All experimental groups recieved their own  specific  programs  for 16 sessions (eight weeks), each session 90 minutes long.Results: kruskal Wallis analysis indicated that there was a significant difference (x2=60/8) among all three experimental groups. The result showed that the integrated method was more effective than the two other ones. Conclusion: This study shows that integration of ABA and PRT is more effective for vocabulary development of four to six year-old children with autism spectrom disorder.