本研究的主要目的在於探討中度智能障礙兒童（以下簡稱智能障礙兒童）與自閉症兼伴中度智能障礙兒童（以下簡稱自閉症兒童）在語彙、語法、語用、以及語言特質方面之異同。研究樣本分智能障礙組與自閉症組。樣本年齡分佈由六至十二歲分二個年齡層，以智商、性別及生理年齡為配對條件，每一組每一年齡層各有六名樣本，合計有二十四名樣本。 研究採用質的研究法，將兩組兒童在各種不同情境（如學校、家庭）的口語表達行為，以錄影拍攝方式蒐集語言樣本，進一步做內容分析 (content analysis)，以瞭解智能障礙兒童與自閉症兒童在語彙、語法、及語用等之表達能力的差異。研究之結果顯示： 一、在語彙表達方面，智能障礙兒童與自閉症兒童皆以主語、述語、賓語之出現最多，其他較抽象詞類之出現很少。但智能障礙兒童較自閉症兒童出現較多的副詞。 二、在語法表達方面，智能障礙兒童與自閉症兒童的簡句的出現率很相近，然相較於智能障礙兒童，自閉症兒童出現較多的不完整句。 三、在工具性、社會性、與個人性之語用方面，智能障礙兒童無論在類別或出現率上，皆較自閉症兒童為多。 四、自閉症兒童較智能障礙兒童出現更多的仿說行為。

　　　　　Previous studies indicate that oral language deficiency is a common problem among children with mental retardation and children with autism, and the magnitude of such impairment is proportional to the severity of mental retardation. The study was to investigate the differences in vocabulary, pragmatics, and syntax between the children with moderate mental retardation and autistic children with mental retardation. Oral language behaviors of studied subjects were videotaped under various natural environments. The language samples were then transcribed for content analysis. The subjects included a group of 12 children with mental retardation and a group of 12 children with autism, aged between 6 and 12. Each group was divided into two subgroups matched by age, sex and IQ. The differences in vocabulary, pragmatics, and syntax were analyzed. The findings of the study are as follows: 1.The most frequently used vocabulary was subject, verb, and object in both groups of mental retardation and autism. In addition, children with mental retardation exhibited more adverbs than autistic children. 2.The group of mental retardation showed the same performance as the group of autistic children in simple sentence. However, children with mental retardation expressed better ability in complex sentence. 3.Children with mental retardation had better ability in instrumental, social, and personal pragmatics than children with autism. 4.Children with autism revealed more echolalia behaviors than children with mental retardation.