Trivia

James Stewart was originally considered for the role Peter Cushing plays in the movie.

Blanca Estrada, Ana Obregon, and Gasphar Ipua are all dubbed, as are many of the supporting actors.

A Spanish-US co-production (copyright 1980), and the only film to feature both Peter Cushing and Paul Naschy, the latter only in for a cameo appearance.

Blanca Estrada is the only actress that dubbed herself on the Spanish version.