The name of the mill is "Bachman Mills." "Bachman" is a pseudonym used by Stephen King, upon whose short story the movie was based.

When John and Jane are in the cafe together, Ippeston sitting in the booth behind them is reading a paperback of "Ben." "Ben" is a story of a socially dysfunctional boy who befriends a rat and uses other rats to extract revenge upon others.

Tom Savini was attached to direct the film in the late 1980's but pulled out due to lack of studio interest.

Co-stars Andrew Divoff and Raissa Danilova later married two years after this film was completed.

The movie was filmed in the village of Harmony, Maine at Bartlettyarns Inc., the oldest woolen yarn mill in the United States (est. 1821). The historic Bartlett mill was renamed "Bachman" for the movie, an homage to King's pseudonym, Richard Bachman. The interior shots of the antique mill machinery, and the riverside cemetery, were in Harmony. Other scenes (restaurant interior, and giant wool picking machine) were at locations in Bangor, Maine, at an abandoned waterworks and armory. A few other mill scenes were staged near the Eastland woolen mill in Corinna, Maine, which subsequently became a Super Fund site.

Wisconsky mentions she is from Castle Rock, home to many other Stephen King books and movies.

The patch on Cleveland's (The Exterminator) shoulder is the emblem of 33 ("Ba Muoi Ba"), a Vietnamese rice-brewed beer that was popular among American GIs who served during the war.

The producers were afraid that the rats would not be terrifying enough, so the talents of a top voice-over artist were added to the sound track.

Warwicks car is a 1960 Cadillac Coupe DeVille.

Jane's car is a 1966 Ford Mustang.

It is unclear whether or not Diet Pepsi's product placement in this film (they allowed cans of Diet Pepsi to be used repeatedly throughout the film as projectiles fired at rats and at the giant creature near the end) proved beneficial to the Pepsi corporation.

Trailer narrated by Percy Rodrigues.

When a rat is thrown into the shredder, the effect was achieved by carrying a real rat to the machine and dropping it into a foam cushioned box in front. Then a fake rat made of cotton with a plastic tail and covered with stage blood is used. When a rat runs from an exterminator's spray (actually plain water), it is responding to the sound of a clicker that signals where his rat chow is. When a soda can is thrown by sling-shot and hits a rat, the can actually hits an area in front of the rat and the rat is pulled out of sight by the trainer, who is unseen by the camera. The vacuum hose sucking up rats is sucking up fake rats. Scenes with the water hose were shot in cuts with real rats then cutting to the fake ones being hosed away. Whenever real rats were in water, trained swimming rats were used and closely monitored. Fake rats were used to portray dead rats. The gigantic mutant monster rat is, of course, a puppet.

The creature is a mutated rat with batwings. The explanation, according to the short story, is that the rats in the subcellar (under the trapdoor) have been living so long in the darkness that they have become blind, lost their hind legs, and grown gigantic, some as high as three feet. There are also what seem to be bats the size of crows that turn out to be more mutated rats that have grown wings but haven't yet lost their tails. The creature who attacks them in the movie is most likely the one described in the story as the magna mater or queen mother. She was totally limbless and as big as a Holstein calf.

Body Count: 10 (9 people, 1 monster).