First Season:
A   An Unearthly Child (*) aka 100.000 AD (**) aka The Tribe of Gum
B   The Daleks (*) aka The Mutants (**)
C   The Edge of Destruction (*) aka Inside the Spaceship (**) aka Beyond the Sun
D   Marco Polo
E   The Keys of Marinus
F   The Aztecs
G   The Sensorites
H   The Reign of Terror
(*) Commonly used title (book, video)
(**) BBC production title
Second Season:
J   Planet of Giants
K   The Dalek Invasion of Earth
L   The Rescue
M   The Romans
N   The Web Planet
P   The Crusade
Q   The Space Museum
R    The Chase
S    The Time Meddler

Third Season:
T     Galaxy 4
T/A   Mission to the Unknown aka Dalek Cutaway
U     The Myth Makers
V     The Daleks' Masterplan
W    The Massacre (of St. Batholomew's Eve)
X     The Ark
Y     The Celestial Toymaker
Z     The Gunfighters
AA    The Savages
BB    The War Machines

Fourth Season:
CC    The Smugglers
DD    The Tenth Planet


Fourth Season (cont'd.):
EE    The Power of the Daleks
FF    The Highlanders
GG   The Underwater Menace
HH   The Moonbase
JJ    The Macra Terror
KK    The Faceless Ones
LL    The Evil of the Daleks

Fifth Season:
MM    The Tomb of the Cybermen
NN    The Abominable Snowmen
OO    The Ice Warriors
PP    The Enemy of the World
QQ    The Web of Fear
RR    Fury from the Deep
SS    The Wheel in Space

Sixth Season:
TT    The Dominators
UU    The Mind Robber
VV    The Invasion
WW  The Krotons
XX    The Seeds of Death
YY    The Space Pirates
ZZ   The War Games


Seventh Season:
AAA   Spearhead from Space
BBB   (Doctor Who and) The Silurians
CCC   The Ambassadors of Death
DDD   Inferno

Eighth Season:
EEE   Terror of the Autons
FFF   The Mind of Evil
GGG   The Claws of Axos
HHH   Colony in Space
JJJ   The Daemons

Ninth Season:
KKK   Day of the Daleks
MMM   The Curse of Peladon
LLL   The Sea Devils
NNN   The Mutants
OOO   The Time Monster

Tenth Season:
RRR   The Three Doctors
PPP   Carnival of Monsters
QQQ   Frontier in Space
SSS   Planet of the Daleks
TTT   The Green Death

Eleventh Season:
UUU   The Time Warrior
WWW   Invasion of the Dinosaurs
XXX   Death to the Daleks
YYY   The Monster of Peladon
ZZZ   Planet of the Spiders


Twelfth Season:
4A    Robot
4C    The Ark in Space
4B    The Sontaran Experiment
4E    Genesis of the Daleks
4D    Revenge of the Cybermen

Thirteenth Season:
4F    Terror of the Zygons
4H    Planet of Evil
4G    Pyramids of Mars
4J    The Android Invasion
4K    The Brain of Morbius
4L    The Seeds of Doom

Fourteenth Season:
4M    The Masque of Mandragora
4N    The Hand of Fear
4P    The Deadly Assassin
4Q    The Face of Evil
4R    The Robots of Death
4S    The Talons of Weng-Chiang

Fifteenth Season:
4V    Horror of Fang Rock
4T    The Invisible Enemy
4X    Image of the Fendahl
4W   The Sun Makers
4Y    Underworld
4Z    The Invasion of Time

Sixteenth Season (The Key to Time):
5A    The Ribos Operation
5B    The Pirate Planet
5C    The Stones of Blood
5D    The Androids of Tara
5E    The Power of Kroll
5F    The Armageddon Factor

Seventeenth Season:
5J    Destiny of the Daleks
5H    City of Death
5G    The Creature from the Pit
5K    Nightmare of Eden
5L    The Horns of Nimon
5M    Shada
(not televised)

Eighteenth Season:
5N    The Leisure Hive
5Q    Meglos
5R    Full Circle
5P    State of Decay
5S    Warriors' Gate
5T    The Keeper of Traken
5V    Logopolis
--    K-9 and Company
(50-minute special)


Nineteenth Season:
5Z    Castrovalva
5W    Four to Doomsday
5Y    Kinda
5X    The Visitation
6A    Black Orchid
6B    Earthshock
6C    Time-Flight

Twentieth Season:
6E    Arc of Infinity
6D    Snakedance
6F    Mawdryn Undead
6G    Terminus
6H    Enlightenment
6J    The King's Demons
6K    The Five Doctors
(90-minute special)

Twenty-First Season:
6L    Warriors of the Deep
6M    The Awakening
6N    Frontios
6P    Resurrection of the Daleks
6Q    Planet of Fire
6R    The Caves of Androzani


Twenty-First Season (cont'd.):
6S    The Twin Dilemma

Twenty-Second Season:
6T    Attack of the Cybermen
6V    Vengeance on Varos
6X    The Mark of the Rani
6W    The Two Doctors
6Y    Timelash
6Z    Revelation of the Daleks

Twenty-Third Season (The Trial of a Time Lord):
7A    The Mysterious Planet
7B    Mindwarp
7C    Terror of the Vervoids (*) aka The Ultimate Foe (**)
7C    The Ultimate Foe (*) aka Time Inc. (**)
(*) Commonly used title (book, video)
(**) BBC production title

Twenty-Fourth Season:
7D    Time and the Rani
7E    Paradise Towers
7F    Delta and the Bannermen
7G    Dragonfire

Twenty-Fifth Season:
7H    Remembrance of the Daleks
7L    The Happiness Patrol
7K    Silver Nemesis
7J    The Greatest Show in the Galaxy

Twenty-Sixth Season:
7N    Battlefield
7Q    Ghost Light
7M    The Curse of Fenric
7P    Survival

The 1996 television movie Doctor Who (aka Enemy Within) is not indexed.