Calcareous nannofossils are important tools for the biostratigraphy of marine sediments. Over the past two decades, calcareous nannofossil biostratigraphy has developed explosively, largely due to data made available by the Deep Sea Drilling project. Today, calcareous nannofossil biostratigraphy is often the basis for comparison of other biostratigraphic zonation schemes. The late Eocene is a time of global change in climate and in the oceans. It is of great interest to geologists because of documented changes in chemistry, circulation, and sedimentation patterns of the oceans as well as global climatic cooling. These changes had great effects upon the evolution and distribution of marine plankton at this time. This study utilizes close sampling of sediment cores from four globally distributed Deep Sea Drilling Project sites which contain highly diverse assemblages of calcareous nannofossils. This data allows for the construction of high-resolution range charts of late Eocene calcareous nannofossils. Late Eocene nannofossil events were identified and compared to events in other plankton groups, and attempts were made to correlate the nannofossil events with late Eocene climatic and oceanographic events. Late Eocene biostratigraphy was refined through the construction of a new biozone.