The series was one of the first dramas to follow up on the enormous success of the earlier crime show Homicide and dealt with the wide variety of cases dealt with by police in the fictional Melbourne suburb of Yarra Central (modelled on St Kilda).
The series was both popular - winning 10 Logie Awards, including two Gold Logie awards (for Australia's most popular entertainer) for Gerard Kennedy - and critically acclaimed, winning a number of Penguin and Awgie awards for its scripts and actors. After Kennedy decided to leave Division 4, the Nine Network summarily cancelled the series; only one episode was made with his replacement John Stanton.
The opening theme Power Drive was sampled by TISM in their 1998 single Thunderbirds Are Coming Out.
Sen. Det./Det. Sgt. Frank Banner (Gerard Kennedy), a hard, tough man who has become a loner after his pregnant wife, Joy, died during premature child-birth brought on after being terrorised by a criminal (in the first episode, "The Soldiers"); as a result, he tends to bury himself in his work. He respects but sometimes disagrees with his superior, Sergeant Vickers, and although sometimes using roughhouse methods of handling criminals is both a fair man and a conscientious cop. Banner eventually falls in love with and marries an old friend, Jenny Franklin, and in the second-last episode resigns from the Victoria Police for an extended honeymoon and to find a 'safer' occupation.
Det. Sgt./Det. Snr. Sgt. Keith Vickers (Chuck Faulkner), head of the Yarra Central CIB, married with two sons. He often clashes with his younger son Jamie, a university student, over anti-Vietnam demonstrations. His bark is usually worse than his bite, and although he comes across as a very serious person most of the time, he has a dry sense of humour which lends itself to some nice comedy touches.
Sen. Det. Mick Peters (Terence Donovan), the station's third plain-clothes man. Peters has a happy-go-lucky nature and an eye for the ladies. He has a good record with the Victoria Police, although Vickers sometimes has to pull him into line for being too much of a comedian.
Sgt. Andrew "Scotty" MacLeod (Frank Taylor), head of Yarra Central's Uniform Branch. A meticulous man originally from Scotland (hence his nickname "Scotty"), he is married with four daughters (one of whom is kidnapped by a former adversary in episode 214, "Backlash"). Scotty's role is mainly confined to the station charge counter, and he therefore rarely appears in exterior scenes (allowing actor Frank Taylor to live in Sydney and commute to Melbourne for three days of filming a week).
Const. Kevin Dwyer (Ted Hamilton), an ambitious and dedicated cop who is always eager to work with the CIB. Hamilton was sacked from the series for breach of contract (he had filmed a commercial without permission from Crawfords) in September 1973, in the middle of filming an episode. Frantic script rewrites solved the problem of Dwyer's sudden disappearance by explaining that the character had been accepted for a position in the CIB and transferred out of Yarra Central to commence his detective training (noted in episode 225, "All For One"). Because of Hamilton's abrupt departure from the series (and the resulting production disruptions), Dwyer makes several other onscreen appearances until episode 231, but his final full appearance is in episode 229, "Mad About The Boy".
WPC Margaret Stewart (Patricia Smith), who lives with her mother, is a fairly conservative person, but is keenly interested in the reformation of criminals, and is friendly with and has great respect for Banner. Like Scotty MacLeod, the role of Stewart was a static one, allowing Patricia Smith to commute from Adelaide to Melbourne for filming. Stewart resigns from the force to get married in episode 238, "None So Blind".
Det. Tom Morgan (John Stanton), Banner's replacement, a country cop transferred from Bairnsdale to Yarra Central. Morgan only appears in the final episode of Division 4, the Nine Network having cancelled the series after Kennedy left the show.
Constable Roger Wilson (Andrew McFarlane) becomes a recurring character from episode 235, "Maria". A new recruit to the police force (and a bit of a bungler at first), Yarra Central is Wilson’s first posting, and he develops from a green newcomer to a competent constable who soon settles down. This was McFarlane's breakout role, which later led to his being cast in The Sullivans as series heartthrob John Sullivan. In episode 289, "Tell Me Your Troubles My Friend", Wilson receives a transfer to a country posting at Mansfield.
As of February 2017, twelve volumes of this series have been released on DVD through Crawfords/WinTV, representing the entire series run (with the exception of episode 102A "Conspiracy", which exists as a partial episode only and was not included).