OBJECTIVE The purpose of this study is to expand validity and reliability analysis of Turkish Version of Childhood Autism Rating Scale (CARS), whose internal consistency,content validity and discriminant validity for a limited size of sample group were examined by Sucuoğlu et al. METHODS 96 children and adolescents aged between 4-18, (48 diagnosed with pervasive developmental disorder (PDD) and 48 diagnosed with mental disability (MD) and developmental delay based on DSM-IV-TR criteria,) were included in the study. Regarding reliability analysis of Turkish Version of the scale; Cronbach's alpha values as internal consistency indicator, inter-rater reliability, and test-retest reliability were calculated. Principal components analysis and Varimax rotation were used in order to determine factors. The scale was compared with Autism Behavior Checklist and Clinical Global Impression-Severity of Illness. The most appropriate cut-off point was determined for CARS by conducting ROC analysis. RESULTS As a result of principal components analysis and Varimax rotation, one component factor was obtained. Correlations between CARS and the other scales were statistically significant. The Cronbach's alpha value of total score of the scale was determined as 0,95. Test-retest reliability (r=0,98, p<0,01), and inter-rater reliability (r=0,98, p<0,01) were determined for total score of the scale. The cut-off point of the scale was 29,5. CONCLUSIONS All of these results support that the scale adapted into Turkish is a valid and reliable assessment instrument.