On Wenley Moor, a secret Derbyshire atomic research center where a reactor converting nuclear energy to electrical power is being developed, work is being held up by inexplicable power losses and breakdowns among staff. The Doctor traces the trouble to underground caves where prehistoric monsters live with a nest of highly intelligent man-like reptiles, the Silurians. They went into hibernation millions of years ago but have been resuscitated by accidental electric discharges from the research center. They now claim back 'their' Earth.  The Doctor strives for harmony between Man and Silurian and first seems to succeed with the old Silurian. But then the rebellious and intolerant Young Silurian releases a terrible disease that will wipe out Humans. The Doctor finds an antidote.  The Silurians take over the research center and plan to destroy the Van Allen Belt, which shields Earth from the Sun. The reptiles are tricked into returning to their caves by the threat of radiation and the Brigadier - to the Doctor's disgust blows then up.
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The Doctor:  Jon Pertwee
Dr. Liz Shaw: Caroline John
Brig. Lethbridge-Stewart: Nicholas Courtney

Guest Appearances:
Spencer: John Newman
Davis: Bill Matthews
Dr. Lawrence: Peter Miles
Baker: Norman Jones
Miss Dawson: Thomasine Heiner
Dr. Quinn: Fulton Mackay 
Roberts: Roy Branigan
Dr. Meredith: Ian Cunningham
Hawkins: Paul Darrow
Silurian Scientist: Pat Gorman
Old Silurian: Dave Carter
Young Silurian: Nigel Johns
Silurians: Paul Barton, Simon Cain, John Churchill
Silurian Voice: Peter Halliday
Doris Squire: Nancie Jackson
Squire: Gordon Richardson
Hart: Richard Steele
Travis: Ian Talbot
Masters: Geoffrey Palmer
Robins: Harry Swift
Doctor: Brendan Barry
Wright: Derek Pollitt
Corporal Nutting: Alan Mason
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Producer:   Derrick Sherwin, Peter Bryant (uncredited).
Script Editor: Terrence Dicks.
Assistant Editor:  Trevor Ray (uncredited)
Writer: Robert Holmes.
Director: Derek Martinus.
Designer: Paul Allen. 
Costume: Christine Rawlins.
Make up: Cynthia Goodwin.
Visual Effects: John Horton.
Music : Dudley Simpson. Featured "Oh Well (Part One)" by Fleetwood Mac.
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Novelised as "Doctor Who And The Silurians" by Malcolm Hulke  (0 426 11471 X) first published as "Doctor Who and The Cave Monsters" by Universal Tandem (became W. H. Allen) in 1974 with cover by Chris Achilleos.  New edition in 1992 by Virgin Publishing Ltd. with cover by Alister Pearson.  Target library number 9.

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Released as "Doctor Who and The Silurians" in the UK (BBCV 4990) first released in 1993 with electronically restored color as a double-tape, Also released in Australia & New Zealand (BBC catalogue #4990) on single tape. US & Canada release in 1995 (CBS/FOX catalogue #8256, reclassified as WHV #E1278) as a double-tape release. Cover by Andrew Skilleter. .

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This story was actually titled "Doctor Who and The Silurians".
This was the first story made on color videotape.
This story saw the debut of the Silurians, also known as Earth Reptiles, and the Doctor's yellow roadster, "Bessie".

All seven episodes exist as the PALD3 restorations, the original NTSC U-matic dubs and the monochrome telerecordings. Only the black & white film telerecordings were retained in the UK as recovered from BBC Enterprises in 1978.

Studio recording in TC1. (15, 21-22, December 1969; 5, 12 January 1970)
Studio recording in TC3. (8 December 1969)
Studio recording in TC8. (19, 26 January 1970)
Marylebone Station, Melcombe Place, Marylebone, London, NW1. (12, 24November 1969)
Melcombe Place, Marylebone, London, NW1. (12 November 1969)
Dorset Square/Balcombe Street, Marylebone, London, NW1. (12 November 1969)
Walkway by Swanscombe House, Edward Woods Estate, corner Queensdale Crescent and St. Ann's Road, Shepard's Bush, London, NW11. (12 November 1969)
Sheephatch Farm, Sheephatch Lane, Tilford, Surrey. (13-14 November 1969)
Hankley Common Ministry Of Defence Base, Rushmoor, Surrey. (17-18 November 1969)
Milford Chest Hospital, Tuesley Lane, Milford, Surrey. (19 November 1969)
High Street, Godalming, Surrey. (20 November 1969)
Hog's Back Transmitter Station, Hog's Back, Guildford, Surrey. (20 November 1969)

Episode 1 - When Major Baker leaves his security conference with the Brigadier (after the Brig says the Doctor is his personal responsibility), Norman Jones can't get his briefcase to shut properly and has to walk out holding it closed with both hands.
Episode 1, 2, 5 - In episode 1 Liz's belt is tied to her left, but in episode 2 it's tied to her right. In episode 5, when she has that same outfit on again, the belt's back to being tied to her left.
Episode 3 - When Dr. Quinn turns up at Squire's farm it's raining heavily, unlike all the other outdoor scenes in this episode. In the next scene in the barn, he starts with his jacket soaking wet, up until the Doctor's line, "I understood you weren't feeling too well". From that point onward, Quinn's jacket is suddenly completely dry.
Episode 5 - When the Old Silurian is talking to the Doctor in the control room, the headpiece of his costume is loose, and the piece of white tape (or velcro?) meant to hold it attached to his body is very visible.
Episode 5 - As a Silurian prepares to revive Major Baker in the caves, the actor catches his foot on some kind of cable lying on the floor of the set. Then, when Baker wakes up and moves off, the fiberglass rock on which he was lying wobbles noticeably.
Episode 6 - Another loose Silurian headpiece, this time on the Young Silurian, as he commands the removal of the Old Silurian's body.
Episode 6 - After ranting to Liz about the complaints he intends to make to the Brigadier, Dr. Lawrence brushes past him in the doorway of the conference room without a word!
Episode 6 - The Silurians burst into the cyclotron room and start killing the technicians before the Doctor stops them. As one Silurian turns to face the Doctor, his third eye keeps flashing for an extra few seconds.
Episode 7 - It is explained that the Van Allen belt protects Earth from harmful radiation, but in reality it's the ozone layer that performs this function.
Episode 7 - The Doctor sets the reactor to overload and the Silurians make a dramatic exit – except, where do they walk off to? The only exit from the cyclotron room is by way of the raised outer control room, but the humans watch the Silurians walk away from that. To all appearances they just vanish off the set.