On the DVD these interesting facts were told by the directors and writers: the character Adam is actually the co-writer of Saw. The Saw was only shot in 18 days and under 1,000,000 dollars, and it all took place in 2 warehouses and the writers/directors came up with the idea by wanting to make a movie that revolves around a single room and the people trapped inside.

The intestines that are seen being used in Amanda's trap were real pig intestines.

As mentioned on the DVD commentary, Amy Lippens, the casting agent, asked James Wan, the director, which actress he's interested in for the role of Amanda. Wan suggested Shawnee Smith, whom he had a crush on since he was a teenager. A few days later, when Amy Lippens told him that they actually signed Shawnee, he was happily surprised.

The budget did not allow for a dummy of Jigsaw to be made, so actor Tobin Bell had to lie on the floor and portray his character in each shot the body appears in.

In the scene that Amanda digs through her cellmate's innards for a key, the hands shown in the close-up shot are not actually Shawnee Smith's hands at all. They're Leigh Whannell's hands with his nails painted black. Likewise, several shots of Detective Sing (when he first enters Jigsaw's lair and when he is killed by the hidden shotguns) it is not actually Ken Leung but Whannell dressed as Leung's character.

Adam's screams, which are heard during Lawrence's successful effort to saw off his foot, are the exact ones heard when he is being sealed in the room by John/Jigsaw. It's the same audio file.

The director and writer were also the director and writer of a low budget Australian film called Stygian. There is even an inside joke when someone at one point refers to "Stygian Street" and you see the street sign.

Shawnee Smith spent only one day on set.

There were no effects added to Tobin Bell's voice on the recordings, save for slowing it down.

According to an interview with Leigh Whannell, Adam and Lawrence were originally going to be trapped in an elevator, not the infamous bathroom.

The music that starts to play at the end, which has become a signature tune for the twists at the end of the "Saw" films, is titled "Hello Zepp". Though the tape Adam finds actually adresses "Hello Mr. Hindle".

The scene in which Gordon turns off the lights and whispers to Adam was written differently in the script. The characters were to cut open opposite ends of a long pipe with their hacksaws and speak through it. This sequence was actually shot, but later cut because director James Wan decided that the characters being able to cut through a pipe made no sense if they couldn't cut through their chains.

Although never mentioned on-screen, the puppet's name is Billy.

Pre-production for this movie lasted only five days. The bathroom scenes were shot in just six days and the actors' rehearsal takes were used as the actual footage for the film.