The paper describes the major circulation changes in the eastern Indian Ocean during last 5 million years based on variation in planktic foraminiferal assemblages in various ODP and DSDP cores examined by various workers. The Late Miocene/Pliocene transition is characterized by weakening of the Leeuwin Current and migration of the polar front towards north. The early Pliocene is marked by closing of the Indonesian Seaway for surface waters and strengthening of the Leeuwin Current, a general warming of the surface waters and thickening of the mixed layer in the eastern Indian Ocean. The Late Pliocene and Pleistocene witnessed severe climatic fluctuations and episodic weakening and strengthening of the Leeuwin Current in response to either ENSO induced changes in the Western Pacific Warm Pool or lowering of sea level and reduction in Indonesian throughflow due to ice sheet expansion.