Catastrophic mortality of corals due to severe tropical storms, emersion at low tide, salinity changes, excessive siltation, earth movements and by other agencies is discussed. Destruction on a scale unprecedented in recent times of the corals of coral reefs of the Great Barrier Reef and at Guam and Palau due to the feeding activities of the starfish Acanthaster planci is described. Wholesale destruction of corals of coral reefs at numerous other localities in the Indo-West Pacific region due to population explosions of this coral predator appears to have recently occurred or to be occurring. The possibility is raised that unless effective measures to control the starfish plagues are rapidly adopted coral growths on reefs of many areas of the Indo-West Pacific region will be impoverished for prolonged periods.