Though the film was released in America, and even had a paperback, it was not the big success as it was in Spain, where for 1971, it overtook the success of a lot of domestic horror films and firmly established Naschy as a "horror stat." After the personal disappointment of LOS MONSTRUOS DEL TERROR and LA FURIA DEL HOMBRE LOBO, Naschy must have been relieved to have this film work the way he envisioned. His director this time around was Leon Klimovsky, an Argentinian-born cineaste who already had years of experience in directing, both in Argentina and now in Spain.
The United States release is curious, in that a major distributor did not pick it up, but rather a smaller company, First Leisure Entertainment. The music score was changed and the film slightly edited. As Walpugis Night is unknown in America, the film was titled as THE WEREWOLF VS. THE VAMPIRE WOMAN. It was not a tax shelter, however, and was shown across the country. The film also had a poster and photos, and that paperback (which had little to do with the film). Despite its nationwide showing, this American version has not yet seen an authoritative release on DVD or Blu-Ray.
The authoritative European version was released on DVD, as WEREWOLF SHADOW, by Anchor Bay in 2002. This DVD was not the First Leisure edit. Germany did a Blu-Ray version, containing an English track, and it is this German release that is illegally copied by American bootleggers. Yes, Blu-Rays can be duplicated.