Mergen, Kestel and Kayran tributaries of Büyük M endere^river are studied in order to find out their ancient ibeds and to see whether gradients of these .beds can be taken as bases for regulating profile. Longitudinai and cross profiles of streams and watersheds are derived from maps. By interpreting these profiles, four different ancient beds are determined and it is concluded that their gradients can be accepted as regulating gradients.