Protoperidiniacean dinoflagellate cysts have been recovered from Upper Miocene sediments of Hole 1095, ODP Leg 178, drilled to the west of the Antarctic Peninsula. These cysts make up virtually the entire dinoflagellate cyst assemblages, and three new species are formally described herein as Selenopemphix bothrion sp. nov., Selenopemphix kepion sp. nov. and Selenopemphix minys sp. nov., together with one informal taxon and two species attributed to published taxa. The occurrence of Late Miocene protoperidiniacean-dominated assemblages in the vicinity of the Antarctic continent is of special interest. Their presence may indicate the initiation of the Antarctic Circumpolar Current and increased nutrient supply within the Southern Ocean as the Antarctic Divergence became established. A comparison with several other protoperidiniacean dinoflagellate assemblages of similar age in other parts of the world rovides some preliminary evidence for possible concomitant oceanographic change at this time.