Helena Fernán-Gómez was dubbed in post-production by Pedro Almodóvar, because he could fake a more feminine voice that Zulueta wanted for the character.
The final sound of the machine gun was an idea by Eusebio Poncela. He has express his regret later for that suggestion, arguing the other idea of Iván Zulueta was better and gave the ending a different meaning.
Editing took 6 months, and the first cut was 180 minutes. Producer Augusto Martínez Torres loved it but knew it was impossible to premiere like that. After battling a bit with Iván Zulueta, they managed to produce the final cut, which is 110 minutes long.
Both the shooting schedule and the budget grow over the production.
Some sources say the movie had a limited premiere on March 02 1979. At the beginning of the movie, when José drives his car, a theatre marquee announces "Voyage au bout de l'enfer (1978), 5th month". Voyage au bout de l'enfer (1978) was premiered in Spain on March 19 1979 (17 days after the supposed limited premiere of this movie), so that scene had to be filmed in August 1979. Another theatre announces Superman (1978), which was released in Madrid (Spain) on February 08 1979, less than a month before the supposed limited premiere. By other way, in that scene re-release of other movies appear in other theaters marquees, which were in that theaters during that summer of 1979, but not before.