Jose Antonio Valdelomar González (Pablo) was recruited by Saura in a casting for non-professional actors. He was paid US$3,000. In 1992 he was found dead of a heroin overdose at Carabanchel prison (Madrid), where he was arrested for robbing a bank.
The flat that appears in the film is near Vallecas Villa RENFE Station. The building is still there. But now there are roads and gardens surrounding the place.
You can find the place writing this in Google Maps: 40.382615,-3.620963
Despite false rumors that she died of an overdose, Berta Socuéllamos (Ángela) gave up everything for her privacy and she lives in peace with her family. She married 'Jose María Hervás' (el Sebas) and they still live in the same place
Rumor has it that most of the cast were real life heroin addicts and that they were paid with heroin so they wouldn't leave the movie. Enrique San Francisco claims this is true.
The soundtrack song "Me quedo contigo" is played by Los Chunguitos, a famous Spanish gypsy rumba group.