Dennis Franz (Detective Andy Sipowicz) is the only actor to appear in all 261 episodes of the series. In second place is Gordon Clapp (Detective Greg Medavoy), who appears in 256 episodes.
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 Il tenente Kojak (1973).
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 E.R. - Medici in prima linea (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 E.R. - Medici in prima linea (1994).
Just like an earlier Steven Bochco series, Hill Street giorno e notte (1981), most of the episodes were written to take place over the course of a single day.
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.