About twenty ammonite species of Turonian age were determined from several sections in North-East Bulgaria. Six of them–Subprionocyclus hitchinensis, Mesopuzosia beloensis, Tongoboryoceras donovani, Tongoboryoceras rhodanicum, Gaudryceras denseplicatum and Anagaudryceras sacya were found for the first time in Bulgaria. The three Turonian substages are biostratigraphically proven. Three „standard ammonite zones“ (uppermost Early Turonian–Mammites nodosoides Zone, Middle Turonian–Collignoniceras woollgari Zone and Late Turonian–Subprionocyclus neptuni Zone) are established. The lower-middle and middle-upper Turonian boundaries are estimated by ammonites.