Some parents have complained to the BBC that Doctor Who is too scary and has frightened their young children.
Episode three, shown last Saturday, sparked criticism from parents as it showed aliens who possess dead bodies.
But the BBC said people expect Doctor Who to be scary and they took care to make sure it was suitable for kids.
"Doctor Who is a family show and always will be. It has a history of being entertaining and scary - that is what viewers expect," a BBC spokesman said.
The spokesman added that the BBC left it up to parents to decide whether or not Doctor Who is suitable for their children.
And that trailers were shown regularly for each episode to make it clear what the content of the programme was.
The new series of Doctor Who started on the BBC in March, starring Christopher Eccleston and Billie Piper.