Dennis Franz (Detective Andy Sipowicz) is the only actor to appear in all two hundred sixty-one episodes. Gordon Clapp (Detective Greg Medavoy) holds the number two spot, appearing in two hundred fifty-six episodes.

Ricky Schroder (Detective Danny Sorenson) left the show because his wife suffered a miscarriage and felt he needed to return home with her, so they wrote him out.

The exterior of the 9th Precinct station house is used to represent the fictional 15th Precinct's station house. It is the same building used to represent the station house on Kojak (1973).

Sharon Lawrence later got married in the same church where her character Sylvia's wedding was filmed.

The man we see playing the violin just before the closing credits of this show (and most other Steven Bochco productions) is Bochco's father. They computer animated a portrait of him to make it appear he's playing the violin.

According to Steven Bochco, Sherry Stringfield asked the producers to release her from her contract after the first season because she said she was not enjoying being a television actress and wanted to return to New York City. Less than a week after being let out of the contract, she was hired as a regular cast member for the new television series ER (1994). However, in his book "True Blue", David Milch said that Sherry's contract-end request came about because she had very little to do, the prominence of Andy Sipowicz's relationship with Sylvia Costas, took all of the story time that was originally intended for scenes between David Caruso and Sherry, and the request was amiably granted, with Milch also stating he was happy when she got a prominent role on ER (1994).

Just like an earlier Steven Bochco series, Hill Street Blues (1981), most of the episodes were written to take place over the course of a single day.

John F. O'Donohue (Detective Eddie Gibson) was a real-life N.Y.P.D. Detective before retiring to pursue an acting career.

Prior to the show's premiere, and immediately afterward, there was enormous controversy over what was perceived to be high levels of offensive language and nudity. Many affiliates refused to air the show and several advertisers boycotted it. Steven Bochco negotiated intensely with the network for a certain amount of language and nudity to be allowed. He has said that because of the pressure on the network from this criticism, the show would likely not have survived, had it not been an instant hit.

Dennis Franz (Detective Andy Sipowicz) and Gordon Clapp (Detective Greg Medavoy) are the only actors to appear in all twelve seasons.

The character of Detective John Kelly was originally named Flinn, and intended for Jimmy Smits, who turned down the role. Smits later played Kelly's replacement, Detective Bobby Simone.

The character "Andy Sipowicz" was ranked number thirty-one in TV Guide's list of the "50 Greatest TV Dads of All Time" (June 20, 2004 issue).

Despite having appeared on the show since the second season, Scott Allan Campbell's character Internal Affairs Bureau Sergeant Martens did not get a first name (Jerry) until the final season.

The footage of the Chinese parade (dragon, fireworks, and drums) that's shown in the opening credits was used in the opening scenes of Year of the Dragon (1985).

The sets on this show of the "New York streets" were on the backlot of Twentieth Century Fox, and were originally built for Hello, Dolly! (1969). Some location work was actually done in New York City for most of the show's run, mixing specific scenes with general location footage that was used for between-scenes and opening-credits sequences. During the final seasons, however, the combination of high costs for location filming and the show's reduced ratings meant that one hundred percent of filming was done in Los Angeles.

Before joining the cast as Detective Connie McDowell, Charlotte Ross appeared in the fifth season as the abused wife of a cop suspected by Detective Bobby Simone (Jimmy Smits) and Detective Diane Russell (Kim Delaney) of killing a prostitute. When Andrea Thompson left the series, Producer Steven Bochco remembered Ross, and wrote the part of McDowell for her.

Jimmy Smits left the show once his initial contract ended. During the show's run, he found the constant last-minute re-writes frustrating and chose not to extend it, but stayed on for a five-episode arc at the beginning of season six to allow his character have an explained departure.

Before joining the cast as Lieutenant Thomas Bale, for the twelfth season, Currie Graham appeared in season four, episode twenty, "Emission Impossible", as a street punk murderer.

Jimmy Smits and Kim Delaney appeared in The Broken Cord (1992).