The OO Section of the British Secret Service is undoubtedly one of the most exclusive "clubs" in the world, consisting of a handful of agents who have earned the coveted "licence to kill" in the line of duty.

According to the books, there are only three OO Agents at any given time. According to the movies, there are nine at any given time. Below is a list of OO Agent appearances. The list is broken up into books and then movies.

BOOKS:
004 - In The Facts of Death, after M's lover is killed, Bill Tanner is about to call 004 to the scene. M overrules him and asks for 007.
005- In Colonel Sun, Stuart Thomas is head of Station G. He had long served as 005 until his eye began to have troubles, thus impairing his use of firearms. By the end of the book he is assumed dead. In The Facts of Death, however, he is seen again. Obviously it was premature to assume he was dead.
006- In On Her Majesty's Secret Service the OO Section gets a new secretary, Mary Goodnight. The section lays bets on who will be the first to seduce her. 006 is mentioned as the equal favorite with 007.
008- In Moonraker 008 is mentioned as resting in Berlin after a mission. He is named only as Bill. In Goldfinger, 008 is mentioned by Bond as the person who will most likely replace him if he is killed.
009- In Thunderball, when Bond is sent to a health clinic, M puts 009 in charge of the OO Section.
0011- In Moonraker, 0011 disappeared in Singapore and had been missing for two months.
0012- In The World is Not Enough, James Bond avenges 0012's death in the opening scene.

MOVIES:
002- In The Man With The Golden Gun it is revealed that Bill Fairbanks, 002, was assassinated in Beirut by Francisco Scaramanga in 1969.In The Living Daylights, 002 is a different man (it is assumed he is Bill's replacement) who is captured during a training mission in Gibraltar.
003- In A View to a Kill, 003 is found dead in the Siberian ice by 007.
004- In The Living Daylights 004 is assassinated by a Russian agent during a training mission on the island of Gibraltar.
006- In Goldeneye, Alec Trevelyan is listed dead by MI6 at the hands of Soviet Colonel Ourumov during a mission with 007 to blow-up a Soviet nerve gas factory. He resurfaces as Janus, and is killed by 007.
007- James Bond; duh.
008- In Goldfinger Bond mentions 008 as his replacement, should he be unable to complete his mission. In The Living Daylights M threatens to replace 007 with 008.
009- In Octopussy 009 is assassinated in West Berlin by a circus knife-thrower after stealing a Faberge egg. In The World is Not Enough, a different 009 is mentioned as putting a bullet in Renard's head, but not killing him.
0012- Technically unnamed in the film, the novelization of The World Is Not Enough has Bond avenging his death in the opening scene. On screen he is simply referred to as an agent.

In addition, the movie Thunderball has Moneypenny state that "every Double-O man in Europe" is in the conference room, and Bond arrives as the ninth agent to be briefed. Whether this means that the agents are 001 through 009 or not is never stated, as it COULD be 002 through 0010, for instance, and perhaps we should consider that some Double-O's were not in Europe and missed the meeting.