Milk yield is important in breeding studies because it is one of the economically important traits. Therefore, determining the relationship between milk yield and some other traits could provide some important easiness in animal breeding studies. In this study, the aim was to evaluate the relationship between mature age milk yield and 9 independent variables (cow age, first mating age, lactation order, lactation period, dry period, first calving age, calving season, birth type and sex of calf) using CHAID analysis. Seven hundred and seventy Brown Swiss animals' records (from 1987-1997) taken from Mus State Production Farm (in Turkey) were utilized. CHAID analysis results showed that lactation period was primary, sex of calf and cow age were secondary and first mating age and dry period were the tertiary variables affecting mature age milk yield.