By my reckoning (some are questionable), there have been **23 voluntary, 8.5 forced, 5 deaths and 1 unknown** (Ace). If you consider death a forced exit, then it's around a third forced and two thirds voluntary (most often for love). ### 1st Doctor * Susan wants to leave (she falls in love), but decides that she can't (because she has to look after her grandfather). The Doctor [forces her out][1] because he knows that it's best. * Barbara and Ian were kidnapped by the Doctor. They [leave voluntarily][2] (the Doctor opposes it) when they find a way to get home. * Vicki falls in love and [leaves voluntarily][3]. * Steven [leaves voluntarily][4] in order to lead a peace effort. * Katarina [dies][5] (sacrifices herself to save the Doctor). * Sara Kingdom (dubiously a companion) [dies][5] by accident. * Dodo [leaves voluntarily][6] (with no real reason given). 5.5 voluntary exits, and 2 deaths. ### 2nd Doctor * Polly and Ben join the 1st Doctor by accident. They [voluntarily leave][7] when they have a chance to resume their normal lives. * Jamie and Zoe are [forced to leave][8] by the Time Lords. (Jamie potentially came back in "[Season 6b][9]", and his second departure is unknown; given that the Doctor still ends up exiled to Earth, Jamie likely was forced to leave again). * Victoria [leaves voluntarily][10] to live a normal life (much the same as Martha) 3 voluntary exits, and 2 forced. ### 3rd Doctor * Brigadier Lethbridge-Stewart played a similar role to a companion, but the Doctor left him, so doesn't really count for this question (and he died well after this). The same is true for Sergeant Benton and Mike Yates. * Liz Shaw never travelled in the TARDIS, but was essentially a companion. She [voluntarily left][11] UNIT (with no real reason given). * Jo [leaves voluntarily][12] (she falls in love). 2 voluntary exits. ### 4th Doctor * Sarah Jane Smith is [forced to leave][13] when the Doctor is summoned to Gallifrey. * Harry [leaves voluntarily][14] to resume his normal life. * Leela [leaves voluntarily][15] (she falls in love). * K-9 (Mk I) [leaves voluntarily][15] (to stay with Leela) and K-9 (Mk II) is [given to Romana][16] (he can only survive in E-Space). K-9 (Mk III) and K-9 (Mk IV) didn't travel with the Doctor. * Romana [leaves somewhat voluntarily][16] (she chooses between staying in E-Space and returning to Gallifrey, rather than either and staying with the Doctor). 4 voluntary exits, and 2 forced. ### 5th Doctor * Adric [dies][17] (saving Earth). * Nyssa [leaves voluntarily][18], much like Steven. * Tegan [gets left behind by mistake][19] once (but rejoins the Doctor after an Earth year), but eventually [leaves voluntarily][20], when she realises she cannot handle life with the Doctor. * Turlough [leaves voluntarily][21] (when he finds out his home planet has improved). * Kamelion [is destroyed by the Doctor][21] when he is again taken over by the Master. 3 voluntary exits, and 2 deaths. ### 6th Doctor * The Doctor is [forced to abandon Peri][22], and he thinks that she has died (it's later [revealed][23] that she did not). 1 forced exit. ### 7th Doctor * Mel [leaves voluntarily][24] for another type of travel. * We don't know about Ace, because the series was cancelled before we found out. Apparently the intent was for her to leave (presumably voluntarily) to train to become a Time Lord. 1 voluntary exit. ### 8th Doctor * Grace declines to travel with the Doctor (a voluntary exit before anything even starts!), although it's questionable whether she can be considered a companion. 0.5 voluntary exits. ### 9th Doctor * Adam Mitchell was [forced out][25] by the Doctor after not even one episode. * Jack Harkness is [left behind][26], although after *Utopia* he voluntarily returns to Torchwood. 2 forced exits. ### 10th Doctor * Rose is [forced to leave][27] (although she does actually stay with a Doctor). * Mickey Smith leaves voluntarily (multiple times!). * Martha [leaves voluntarily][28] to live a (somewhat) normal life. * Donna is [forced to leave][29] because she cannot survive knowledge of the Doctor. The 10th Doctor also had several 'one-off' companions - most lists include them as companions although they never travelled with the Doctor and only appear in a single episode. None of them can be considered to have "left" the Doctor, although two do die (Astrid Peth and Adelaide Brooke), one of whom probably would have travelled with the Doctor. 2 voluntary exits, 1.5 forced, and 0.5 deaths. ### 11th Doctor * Amy and Rory [leave unwillingly][30] after a Weeping Angel sends Rory to 1930s New York, and Amy willingly chooses to be sent back along with him. The Doctor reading their tombstone creates a fixed point in time, so the Doctor is unable to rescue them. * River is fairly similar to a companion, although we haven't seen her really travelling with the Doctor. [Her final appearance][31] in _Name of the Doctor_ is after her [official "death"][32] in "Forest of the Dead". She has not appeared since, and is rather difficult to categorize due to her timeline not quite matching the Doctor's own. In my opinion Craig Owens isn't a companion, although he plays a similar role in an episode. 3.5 deaths. ### 12th Doctor * Like the Brigadier, Danny Pink never travels with the Doctor, but does play a similar role as a companion. [He is killed][33] when he is hit by an automobile, turned into a Cyberman, and eventually sacrifices himself to destroy the rest of the Cybermen, and sacrifices his return journey from the Nethersphere to send back a boy he killed during his time as a soldier. SEASON 9 SPOILERS BELOW * >! in the season 9 finale, [Clara Oswald is killed][34], then brought back between 2 heartbeats using Time Lord technology. She tricks the Doctor in forgetting about her, then [leaves voluntarily][35] for an adventure together with Ashildr in a stolen TARDIS. She will eventually have to return to her final moment so she can die. >! Ashildr is similar in companionship to Craig Owens: the Doctor is involved in multiple episodes with her, but she never actually travels with the Doctor in his TARDIS. in my opinion, she is not a full companion. 1 death, >! 1.5 deaths and 0.5 voluntary exits including Season 9 SEASON 9 SPOILERS END HERE The above only includes companions who appeared on TV episodes (and the 8th Doctor movie); those that appear only in spin-off media (audio dramas, novels, etc) are not included. The [TARDIS Index File][36] has more information about the companions, including the fate of these additional companions. [1]: http://en.wikipedia.org/wiki/The_Dalek_Invasion_of_Earth [2]: http://en.wikipedia.org/wiki/The_Chase_%28Doctor_Who%29 [3]: http://en.wikipedia.org/wiki/The_Myth_Makers [4]: http://en.wikipedia.org/wiki/The_Savages_%28Doctor_Who%29 [5]: http://en.wikipedia.org/wiki/The_Daleks%27_Master_Plan [6]: http://en.wikipedia.org/wiki/The_War_Machines [7]: http://en.wikipedia.org/wiki/The_Faceless_Ones [8]: http://en.wikipedia.org/wiki/The_War_Games [9]: http://en.wikipedia.org/wiki/Season_6B [10]: http://en.wikipedia.org/wiki/Fury_from_the_Deep [11]: http://en.wikipedia.org/wiki/Inferno_%28Doctor_Who%29 [12]: http://en.wikipedia.org/wiki/The_Green_Death [13]: http://en.wikipedia.org/wiki/The_Hand_of_Fear [14]: http://en.wikipedia.org/wiki/Terror_of_the_Zygons [15]: http://en.wikipedia.org/wiki/The_Invasion_of_Time [16]: http://en.wikipedia.org/wiki/Warriors%27_Gate [17]: http://en.wikipedia.org/wiki/Earthshock [18]: http://en.wikipedia.org/wiki/Terminus_%28Doctor_Who%29 [19]: http://en.wikipedia.org/wiki/Time-Flight [20]: http://en.wikipedia.org/wiki/Resurrection_of_the_Daleks [21]: http://en.wikipedia.org/wiki/Planet_of_Fire [22]: http://en.wikipedia.org/wiki/Mindwarp [23]: http://en.wikipedia.org/wiki/The_Ultimate_Foe [24]: http://en.wikipedia.org/wiki/Dragonfire_%28Doctor_Who%29 [25]: http://en.wikipedia.org/wiki/The_Long_Game [26]: http://en.wikipedia.org/wiki/The_Parting_of_the_Ways [27]: http://en.wikipedia.org/wiki/Doomsday_%28Doctor_Who%29 [28]: http://en.wikipedia.org/wiki/Last_of_the_Time_Lords [29]: http://en.wikipedia.org/wiki/Journey%27s_End_%28Doctor_Who%29 [30]: http://en.wikipedia.org/wiki/The_Angels_Take_Manhattan [31]: http://en.wikipedia.org/wiki/The_Name_of_the_Doctor [32]: http://en.wikipedia.org/wiki/Forest_of_the_Dead [33]: http://en.wikipedia.org/wiki/Dark_Water_(Doctor_Who) [34]: https://en.wikipedia.org/wiki/Face_the_Raven [35]: https://en.wikipedia.org/wiki/Hell_Bent_(Doctor_Who) [36]: http://tardis.wikia.com/wiki/Companion