ABSTRACT: We present the most complete record of Rupelian to Chattian hyaline larger foraminifera inMediterranean Tethys from Keleredere section (Mu region, eastern Anatolia) based on the biometric study of such stratigraphically important groups as Miogypsina, Miogypsinoides, Nephrolepidina, Eulepidina, Nummulites, Cycloclypeus, Heterostegina, Operculina and Spiroclypeus. The identified taxa, most of which are described for the first time in Turkey and represent the Shallow Benthic Zones 22A, 22B, 23, enable us to correlate them with comparativelywell-known coeval taxa from other parts of the Tethys.Our data suggest that the populations of Miogypsinoides, Eulepidina, Nephrolepidina and Cycloclypeus are represented by more than one lineage for each of these groups during Oligocene. Some new taxa such as Nephrolepidina musensis n. sp., Eulepidina anatolica n. sp. and Cycloclypeus pseudocarpenteri n. sp. are introduced. The stratigraphic position of Eulepidina elephantina, highly disputed in previous works, was re-evaluated based on its occurrence in the late Chattian. We for the first time demonstrate the parallel evolution of Miogypsina and Miogypsinoides in the late Chattian of eastern Mediterranean region. Miogypsinoides formosensis is associated with Miogypsina basraensis at the lower part of upper Chattian and this association is accompanied by Miogypsinoides sivasensis at the uppermost part of the section. We compare our results with the available data from other parts of Tethys and remarks on Rupelian-Chattian boundary and the zonation of shallow-marine Oligocene of Mediterranean Tethys are made.