A group of policemen and policewomen from different municipalities are in Rome to take a course that will take them on a study trip to London. Between adventures and misadventures, a parade of television comedians search for a laugh.
New rules enforced by the Lady Mayoress mean that sex, weight, height and intelligence need no longer be a factor for joining the Police Force. This opens the floodgates for all and sundry to enter the Police Academy, much to the chagrin of the instructors. Not everyone is there through choice, though. Social misfit Mahoney has been forced to sign up as the only alternative to a jail sentence and it doesn't take long before he falls foul of the boorish Lieutenant Harris. But before long, Mahoney realises that he is enjoying being a police cadet and decides he wants to stay... while Harris decides he wants Mahoney out!
The crooks in London know how it works. No one carries guns and no one resists the police. Then a new gang appears that go one better. They dress as police and steal from the crooks. This upsets the natural order of the police/criminal relationship and the police and the crooks join forces to catch the IPOs (Impersonating Police Officers), including an armoured car robbery in which the police must help the gangs to set a trap.