The series was a reasonable success in Japan. When it came to the US received a good audience and the distributor changed the opening song. They made a new version using the song "The First Day of Forever" by the band The Mystic Moods Orchestra.
In Brazil, the series was very well received and aired on TV until the beginning of the 1990s. Most of the monsters had their names changed to better suit the sound of the Portuguese language, as follows:
Hedoron became Hidrax;
Gokinosaurus became Mega-Ortópteros;
Nezubirdon became Diplocéfalo;
Neo Hedoron became Medusóide;
Mogunetudon became Silonetaux;
Thunder Gei became Baletrônico;
Bakulah became Gigateris;
Gilagind became Telescópus;
Kuruma-Nikuras became Semaforum;
Baronsaurus became Balu;
Satan King became Belzebu;
Mogz became Doquinodonte;
Salamadar became Salamadra;
Zariganid became Paguróides;
Spincobra became Laminarium;
Mitsuzu-Ryu became Dragão Tricéfalo;
Moonthunder became Celenetério;
Metanodon became Macranuron;
Alien Kyudora became Vurdalak;
Gorda became Saladim;
Great Satan became Lisa, a Feiticeira Rainha de Mefístia (the Witch Queen of Mefístia);
Alien Genos became Eikes;
Deceitman became Super-Monstro.
The most stranger new name was for monster Dokuro, baptized as Tyrannosaurus Rex though it had no resemblance to the famous dinosaur.
Tetsuo Narikawa was a karate master and helped to found the Japanese karate league. Despite this he never used his karate skills in the series. The action scenes with Spectreman were played by Koji Uenishi who also played Kara the gorilla.