An experimental lab animal called a gargantua escapes from his captors and is suspected to be the creature that is killing people all over the countryside. But when the gargantua from the lab appears at the same time as the evil gargantua, the two begin to battle across Japan.

War Of The Gargantuas 1966 (aka Furankenshutain No Kaiju: Sanda Tai Gaira as the Japan title) is one of classic Japanese director's, Ishiro Honda, masterpieces of giant monster madness and mayhem incarnate. A most deadly giant beast is terrorizing the seas and rural Japan, sinking ships, attacking unwary fishermen and people living in the country. Using a sophisticated space age ray super cannon, the Japan military almost kills the huge green monster before its even larger and enormous sized big brother the brown gargantua comes to his rescue. The two garganutas don't agree on how to treat humans and their environment. This inevitably leads to the monster sized duo sibling rivalry of doom. Will Japan and the world survive the War Of The Gargantuas ?