During production, a Boston resident was paid to remove the air conditioner from his window so they could film on that particular street for a shot. The next day when they arrived to continue filming, every window on the street had an air conditioner.
In August 1978, fifteen unedited reels of the film were stolen at gunpoint from a Boston studio in a bizarre movie heist ironic to the film's heist plot. However, the stolen film was mostly outtakes and dailies that could be easily replaced. The positive prints of negatives of the film's footage were actually held by Technicolor in New York City. The robbers demanded a US $600,000 ransom. The money was never paid and the film completed without the missing footage and without any detrimental delays. When the robbers called to demand their ransom, director William Friedkin told them, "Get a projector and enjoy the film. It's all yours!".
Based on the 1950 Brink's robbery in Boston where US $2,700,000 was stolen. A few of the real robbers worked as advisers on the film.
Part of the movie was filmed at the garage where the actual robbery took place. The garage now is just a regular parking garage and no longer is used by Brink's.
When shooting the aftermath of the robbery in the garage where the boys start opening the money bags and frolicking in cash, director William Friedkin did not like the way the prop money looked on film. To remedy this, Dino De Laurentiis wrote a check for approximately $700,000 and had it cashed in 1, 5,10, and 20 dollar bills. The money was then transported to the set in actual Brink's trucks and the scene was shot using real money.