Potassium-argon total-rock ages are presented for extrusive and hypabyssal volcanic rocks of Campbell Island Volcanics, which overlie Cretaceous-Oligocene pelagic marine (Campbell Island Group) and Upper Miocene volcaniclastic sediments (Shoal Point Formation). Ages of basalt, hawaiite, mugearite, and trachyte range from 11.1 to 6.5 Ma, but there is an important concentration at 7.0-7-4 Ma (Upper Miocene). The earliest basalt flows (11.1 Ma), seen only at Puiseux Peak, are overlain by about 300 m of hawaiite-mugearite-trachyte extrusives of alkali olivine basalt type (7.0-7.4 Ma). These in turn are capped by at least 100 m of similar but younger flows (6.5-6.7 Ma) that are best seen on the northern flanks of the island at Mt Faye.