Most of the conversations between Robert De Niro and Joe Pesci were improvised. Martin Scorsese would tell them where to start and where to end. The rest was up to them.
The costume budget for the film was $1 million. Robert De Niro had seventy different costumes throughout the film, Sharon Stone had forty. Both were allowed to keep their costumes afterwards.
The producers said that one of the most difficult things about filming this movie was finding people who would tell them how to cheat in the casino.
Joe Pesci's wife (at the time of filming), Claudia Haro, played Trudy, the co-hostess and band leader of "Ace's High". Haro and Pesci divorced and she remarried. She was convicted in 2000 of two counts of attempted murder for hiring a hitman to try and kill her other ex-husband, a stuntman.
When James Woods heard that Martin Scorsese was interested in working with him, Woods called Scorsese's office and left the following message: "Any time, any place, any part, any fee."
Frank Cullotta: The gray-haired hitman in sunglasses near the end of the movie. He was the Chief Lieutenant of Tony Spilotro in the late 1970s and early 1980s. Cullotta entered the Witness Protection Program before the "cornfield incident" took place and was not present, unlike Marino.