The first Sherlock Holmes movie to be filmed in color.
This film was planned to be the first in a series of many Sherlock Holmes films starring Peter Cushing, produced by Hammer Films. The audience disapproved of a Hammer film without any monsters and failed to turn up. The planned franchise was then dropped.
For his role as Sherlock Holmes he of course had to have a pipe but as Peter Cushing was either a non-smoker or didn't like the taste of the pipe, he kept a glass of milk always to hand to remove the taste.
The hound they used was a real dog called Colonel. On the set before the hound attacks Christopher Lee's character Sir Henry Baskerville, they could not get Colonel to jump on Lee, so they started to 'prod' him into action. Lee gave up and suddenly, Colonel lunged on him and bit right through one of his arms.
Christopher Lee readily admits he has a morbid fear of spiders, and the panic on his face during the scene with the tarantula is not due to acting.