The existence of uncharted seamounts in the Cook-Austral region of the South Pacific has been investigated using GEOS 3 and SEASAT radar altimeter observations. Three previously uncharted submarine seamounts, provisionally named GEOS A to GEOS C, have been located between Mauke and Rimatara and a fourth, GEOS D, has been located east of Rurutu. This confirms that the Aitutaki-Mauke islands of the Southern Cooks are a continuation of the Austral chain. A second group of uncharted seamounts has been provisionally located some 200 km south of Rimatara and Maria and this is suggestive of a second seamount chain, south of the first, that includes Raratonga and Mangaia. Fabert Bank, to the south of Mangaia, appears to be mislocated by about 20 in longitude.