Sir Christopher Lee (Dracula) has only sixteen lines in the entire film, all dispensed by the 10 minute mark.
In 2007, this movie was selected for preservation by the BFI, but it wasn't until 2011 that an extended print, including a longer version of the disintegration sequence, was discovered at the National Film center in Tokyo.
On several occasions, Sir Christopher Lee complained about the contact lenses he had to wear for the shock scenes. Not only were they quite painful, but he couldn't see a thing. While running toward the vampire woman for instance, he even ran too far past the camera on the first take.
Peter Cushing did the stunt where he leaps over a banister himself. He insisted on doing so, against the studio's concerns that he might injure himself.
In the U.S., the title was changed to "Horror of Dracula" to avoid confusion with the classic (Dracula (1931)). This was a real concern since the Bela Lugosi version was still being booked into theaters (through Realart) until the Shock Theatre package of classic Universal horror movies was released to television.