A global holocaust decimates the population of the entire world except for two men and a beautiful woman. Dead bodies litter the streets of a lifeless city. Fleeing the horror, the three survivors take refuge on the fringes of a tropical jungle. In an explosion of sexual tension, the men clash in the pursuit of their desires and engage in an all-out war to possess The Last Woman On Earth. Roger Corman directed this color spectacle in Puerto Rico, back to back with Creature From the Haunted Sea and Battle of Blood Island, another Filmgroup production. It shared much of the same technical crew with both films, and in the case of Creature From the Haunted Sea, the same cast. This was the first produced screenplay for Academy Award-winning writer Robert Towne (Chinatown), who also appears in the film (using the pseudonym Edward Wain) as the young lawyer fighting for control of this sexually charged triangle.

A gangster named Harold (Anthony Carbone), his moll, Mary-Belle (Betsy Jones Moreland), and his lawyer, Martin (Robert Towne), are scuba diving in Puerto Rico when H-bombs wipe out the world. Since these three happened to be underwater at the time, they are the sole survivors and get to wander the empty streets and engage in lots of dialogue about humankind's future. Eventually the men fight over who will mate with Mary-Belle and rebuild civilization. Martin is afraid if she spawns with the thuggish Harold, the world will be repopulated with violent people doomed to a future of more bomb building. On Harold's side is the strong-survive theory of Darwinian natural selection. At least the three get to enjoy some crowd-free shopping before the inevitable showdown. This was the first filmed script by costar Towne (credited as Edward Wain), who would later become the highly respected writer of CHINATOWN and THE LAST DETAIL. Director Roger "King of the Bs" Corman filmed it while on vacation in Puerto Rico, where he also made CREATURE FROM THE HAUNTED SEA with the same cast and crew and produced BATTLE OF BLOOD ISLAND, all on the same trip.