(at around 9 mins) The piece of meat Shirl buys for Simonson is clearly not the same piece Thorn unwraps in front of Sol (at around 23 mins).
(at around 1h 1 min) When Thorn is chasing the assassin; Thorn gets shot in the right leg and it starts bleeding profusely. But in the following scene when he is fighting Tab in his apartment; he kicks Tab numerous times with the right leg as if there is no wound. Not only does the leg show no effect of a wound; the leg is also not showing any blood nor are there any blood stains on the pants. Additionally he walks and exits Tab's apartment without a limp.
When Thorn goes into the bedroom, the drink in his hand switches from a highball glass to a tumbler, then back to a highball glass.
At the apparent age of 50, Thorn should be more than old enough to be able to remember the old, fertile world.
Thorn and Roth share a small apartment in a tenement stuffed with people, many of whom live in the hallways and stairwells. When Roth makes the stew, there's no apparent reaction by anyone to the odor of what must have been the first meal cooked inside the building in many years.
Tab Fielding twice uses a pistol with a silencer attached. The pistol is a .38 caliber, Smith & Wesson Police Special - a revolver. Silencers do not work on a revolver; the gap between the cylinder and the barrel will release the sound of the gunshot.
(at around 1h 1 min) During the riot a woman screams after being shot in the head, an injury which makes it impossible to scream.
(at around 56 mins) Donovan tells Gov. Santini that Thorn spoke to the Priest for twenty minutes, however the conversation actually lasts for less than two minutes.
(at around 1h 17 mins) When Thorn is trying to talk to Sol in the Suicide Room, every time the "Speaking Permitted" sign flashes, the cable plugged into the machine can be seen to alter its position, revealing that, instead of actually flashing, the "light" is simply being edited "on and off".
(at around 1h 26 mins) When Thorn is in the Soylent Green factory, he knocks two factory employees off the catwalk. A stunt mattress can clearly be seen sticking out from underneath the conveyor belt where the second one lands.
(at around 1h 26 mins) When Thorn is fighting with the workman in the Soylent factory, the workman grabs hold of the chain behind him before Thorn tries to throw him over the rail (obviously in order to perform the stunt fall onto the conveyor belt.)
Simonson's assassin kills him with a crowbar. The assassin hits Simonson's head with the right angled end of that crowbar. In doing so, the crowbar would have pierced Simonson's skull and penetrated his brain. Yet, when Simonson falls to the floor, there is NO blood on the floor (the only liquid on the floor is from the drink he was holding when he was assaulted). And when Thorn arrives at a later time, there is still NO blood on the floor. Such a head wound would have produced a considerable pool of blood around Simonson's head.
(at around 1h 27 mins) When Thorn returns from the Soylent factory, he uses a police call box. The phone not wired like all other telephones. However, when Thorn uses a police call box earlier in the film, it is also not wired, suggesting that at least some phones are wireless/cordless.
The MGM "Contemporary Classics" VHS packaging twice erroneously refers to Charlton Heston's character as "Simonson", although of course that is the name of the character played by Joseph Cotten.