The purpose of this study was to identify the reliability and validity of CSBS Infant-Toddler Checklist(The Communication and Symbolic Behavior Scale: Infant-Toddler Checklist), developed by Wetherby and Prizant(2002). The total of 844 mothers and their infants(6~24 month olds) were participated in this study. The responses from infants\' mothers were analysed. Results are as follows: First, The high reliability was identified(Cronbach α=.93). Second, 18 items were extracted and 3 factors were identified: nonverbal expressive behavior, verbal-symbolic behavior, and attention-getting behavior. Finally, there was significant correlation between the CSBS Checklist and MCDI-K, so we have found the criterion validity. According to these results, even though there are minor inconsistency with the original CSBS Checklist, it can be used to assess the communicational ability and to predict the language development in infancy.