Andrey Zvyagintsev says the four main characters of the film represent the four elements: "Earth is Mother, water is Father... the elder brother, Andrey, is air and Ivan is fire. But if you think it's all different, it is."
When pre-production was starting, director Andrey Zvyagintsev told producer Dmitriy Lesnevskiy there was no point in making the film if they couldn't find two boys who were "actors of genius." Zvyagintsev had two assistants who helped him look for actors, one in St. Petersburg and one in Moscow, and visited both cities himself. He found Vladimir Garin in St. Petersburg and Ivan Dobronravov in Moscow, picking them from over 600 contenders.
The budget of the film remains a secret, though in an interview the director and the producer hinted that it was well under $500,000. Director Andrey Zvyagintsev also mentioned that the producers made their money back even before they went with the movie to Venice where it was "discovered".
The trivia item below may give away important plot points.
Andrey was supposed to die in the original script. The actor who played him, Vladimir Garin, died on 25 June 2003, shortly after the shooting of the movie was completed, in a lake not far from the one where the movie was shot. The news of his death was postponed until much later after the movie's premiere and subsequent success in the Venice Film Festival.