MacDonald Volcano, located at the younger end of the Austral Islands chain and discovered in 1967 from teleseismic T waves, has been the site of intense volcanoseismic swarms from 1977 to January, 1984. Three new surveys of its summit, including by scuba divers, have revealed pinnacles reaching 27 m b.s.I., and a variety of fresh features, such as fractures and spatter cones. It is strongly suggested that the summit of the volcano swelled and the pinnacles grew since Johnson's last survey in 1975.