Nightmare In Blood was filmed in 1973.
The theater in Oakland, California that was used as a main location was burned down by an arsonist shortly after production on this film wrapped.
Bob Wilkins, who was, at the time, host of a very popular TV show in the San Francisco Bay Area, Creature Features, a show which the director was a frequent guest on, can be seen smoking his trademark cigar in the protest scene, near the start of the film.
When director John Stanley and his co-producer heard that Kerwin Mathews was working in an antique store in San Francisco, they approached him to play a swashbuckler in the movie within the movie. Kerwin loved the idea and said he would do it.