Synopsis: Atomic and nuclear bomb explosions at the Mercury Nevada test site and at the Bikini test site. Scenes of helmeted military personnel in protective trench during atomic bomb explosion. Various scenes of surface and underground atomic explosions with mushroom-shaped cloud in some cases. Shows testing of various structures, rolling stock, objects and materials for blast resistant qualities before and after explosion. Shows atomic cannon firing and explosion. Aerial view of helicopter in flight lowering measuring device. Army doctors examining patients for radiation effects.