Henry Silva broke Steven Seagal's nose in the final fight scene. Seagal was rushed to the hospital. The next day Seagal was back at work. He stayed up all night icing it, so that he wouldn't get a black eye.

The pictures in the opening credits, including the one of baby Nico, are real pictures of Steven Seagal in his youth.

Steven Seagal declared in an interview that among his first five film roles, Nico Toscani was his favorite character to play.

The sword-fighting sequence was staged using Steven Seagal's own martial arts students.

Steven Seagal's film debut. He also co-wrote and co-produced.

Originally, the film was about corruption on the waterfront in San Francisco. When Andrew Davis and Steven Seagal changed the story, they moved the location to Chicago.

Pam Grier said this movie is one of her favorites because it shows off her acting skills.

Before getting this part, Steven Seagal had to demonstrate his martial arts skills for the studio. He physically dominated his students, which terrified the executives. They didn't know it was staged.

After the film opened, aikido experienced a boom worldwide. Steven Seagal's Los Angeles dojo was struggling before the movie. Afterward, it sold out all its classes.

Steven Seagal personally selected every weapon seen in the film.

When Daniel Faraldo auditioned for his role, Andrew Davis thought he was too small to intimidate Steven Seagal. Seagal suggested Faraldo try to scare him, so he tried to break a chair over Seagal's back. He got the part.

Andrew Davis was hired to direct, because Steven Seagal liked Code of Silence (1985).

Steven Seagal chose the film from a pile of scripts Warner Brothers had been saving for Clint Eastwood. It was re-written to focus on Seagal's actual backstory. Many of his stories have never been confirmed.

It has been reported that Steven Seagal was asked to make the film by his former aikido pupil, agent Michael Ovitz, who believed that he could make anyone a movie star.

Steven Seagal and Daniel Faraldo went on a ride-along with real Chicago detectives to prepare for the movie. Faraldo said Seagal scared the criminals more than the cops did.

Reportedly, some scenes had to be cut for an R rating.

Steven Seagal taught all the actors in the movie to draw their gun his way: fast and clean.

The film has a lot in common with Andrew Davis' Code of Silence (1985). Both movies star martial artists, and are about Chicago cops, corruption, and drug lords.

When the film came out in 1988, the crack epidemic was just hitting Chicago.

Steven Seagal choreographed all of the aikido moves.

Henry Silva also played the bad guy in Andrew Davis' Code of Silence (1985).

Joseph F. Kosala is a real Chicago ex-cop. He has been in seven of Andrew Davis' movies. He was a technical advisor on this film.

Ron Dean and Joseph Kosala both play Chicago detectives. They also played Chicago detectives in the Fugitive.

Due to film schedule constraints, the sequences at "Chicago Summer CES" (Consumer Electronic Show) were actually filmed at the November Comdex (Computer Dealer Expo) in Las Vegas. The film crew carried press credentials and pretended to be a news show filming about the products in the booth.

The movie was filmed between April 27 and June 26, 1987.

The church used in the film was St. Mary of the Angel's on Cortland and Hermitage, built in 1920.

When the Tac team is talking to the F.B.I., the layout of Code of Silence (1985)'s opening scene is drawn on the chalkboard.

In the first trailer for the film, the title is "Nico".

Ron Dean also plays a detective in The Fugitive (1993) and The Dark Knight (2008).

For the score, Andrew Davis hired his favorite musicians, like Frank Zappa's drummer Vinnie Colaiuta and Hiram Bullock on guitar.

Ronnie Barron was a soul singer who was also in Andrew Davis' first movie Stony Island (1978).

After Jackson is shot, Nico goes to her apartment. The old photos visible are Pam Grier's real family pictures, modeling shots, and publicity shots.

In the end credits, the bartender is listed as "C.I.A. Bartender". He was an agent all along.

Steven Seagal actually did ruthlessly break Henry Silva's arm in the climactic battle. There is a picture of the two getting a beer immediately the shoot, before Silva got medical attention.