The main purpose of this research is to make the reliability, validity and norm studies of Cognitive Assessment System (CAS), which was developed by Naglieri and Das in 1997, on 5 years old Turkish children. For this purpose, PASS Theory consisting Planning, Attention, Simultaneous and Successive cognitive processed was introduced first, as Cognitive Assessment System (CAS) is a neuropsychological assessment system which is based on PASS Theory. In the data analyses, for the reliability studies test-retest reliability coefficients, content validity coefficients and standard deviation have been calculated. In the validity studies, content validity construct validity and criterion validity procedures have been carried out. Moreover, in the analysis of the data pertaining to demographic features, "MANOVA" and "Scheffe" tests, and for the norm study descriptive statistics methods were used. By the use of these methods percentile and Standard score pertaining to CAS Basic and Standart Batteries were determined. The results of the research reveal that CAS is a reliable and valid instrument for Turkish population. The results also indicate a similarity with the American sample.