This paper investigates the phenomenon of agglomeration in Turkish manufacturing industries; which by definition takes both industrial and geographical concentration into consideration. For this purpose Ellison and Glaeser index (E-G) of agglomeration is used (Ellison & Glaeser, 1997). After examining the results from the index, the E-G index is decomposed to its components in order to identify any similarities or patterns between different types of industries and also to understand the main factor behind the change in agglomeration patterns over time.