The series suffered from the BBC's lack of a proper archiving policy until 1978. It was BBC policy before 1978 to wipe master tapes and reuse them for other programs, hence saving money and storage space. From a full tally of seven hundred ninety-nine episodes, four hundred sixty-six (broadcast between 1962 and 1974) are thought to no longer exist. Additionally, some color videotaped episodes only survive as monochrome film copies. The final four seasons, broadcast between September 1974 and September 1978, exist in their entirety.
The "Z Cars" theme (traditional folk tune "Johnny Todd") proved to be so popular that Liverpool-based football team, Everton F.C., immortalized it as their theme tune as the teams enter onto the field, a tradition that remains. Elton John enjoyed the theme so much that he also adopted it at the club at which he presided as chairman, Watford.
Before he became famous as a movie star, Michael Caine turned down the part of Police Constable Bob Steele, as he did not want to be typecast in a television series. It went to Jeremy Kemp.
Elisabeth Sladen appeared in three episodes of the series. Producer Ron Craddock subsequently recommended her for the role of Sarah Jane Smith in Doctor Who (1963). She retained fond memories of the series, saying in 2009: "I loved Z Cars. If you see a clip of it now, it still holds up incredibly well - really good actors, great directors, and flying by the seat of your pants. You kept on learning, and there were always places for you to learn, which there aren't so many of for young actors now."
The Ford Zephyrs used in the black and white episodes, were actually primrose yellow. This color showed up better than white, on the older type black-and-white film.