The present understanding of natural lightning is reviewed. Recent research on lightning has been motivated, in part, by the need to protect advanced ground-based and airborne systems that utilize low voltage, solid-state electronics; by the desire to prevent spectacular accidents, such as occurred in 1%9
during the launch of Apollo 12 and in 1987 during the launch of Atlas-Centaur 67; and by the desire to elucidate the physics of one of nature’s most impressive phenomena.