All I can add to what has been said before is, what an excellent series this was. It had to be London Weekend Television's most expensive production at the time, and you could see that every penny appeared on screen. There were shoot-outs, explosions, and fist-fights galore every friday night at 9pm, when the episodes were originally shown during the late '70s and early '80s. The sexist banter between the heroes Bodie and Doyle is typical of the period, but stills remains funny to watch. One episode called 'Klansman', about a British right wing group to which Bodie becomes sympathetic, has to this day never been screened in the U.K. for fear of inflaming racial tensions, which were at their height during the Professionals' five year run. It has however, been transmitted in other parts of Europe.
Due to the media, and the then Tory government's paranoia about 'Video Nasties' and TV violence, a sixth series was never made with the original actors. Unfortunately though, it's creator Brian Clemens, decided to update and resurrect the series about four years ago. It sank without trace.
My fave episode has to be 'Hunter Hunted', in which the heros have to recover a stolen prototype rifle, which has a laser aiming system. This series was truly revolutionary!!!