The biostratigraphic distribution and abundance of lower Oligocene and Miocene to Pleistocene silicoflagellates are documented from Ocean Drilling Program Leg 183 Holes 1138A and 1140A, on the Kerguelen Plateau. The Distephanus speculum speculum forma pseudofibula plexus is found in the upper Miocene of Hole 1138A, but other important biostratigraphic markers are not available for detailed biostratigraphy over portions of the hole. The silicoflagellates of Hole 1140A include a new skeletal morphology, described here as Distephanus speculum speculum forma cylindrus. Silicoflagellate diversity and abundance are variable, with abundant silicoflagellates in the Pliocene and Pleistocene, but with some intervals in the Miocene of Hole 1138A being either barren of silicoflagellates or containing only limited numbers.