The charity's full legal name has changed from the Royal Society of Mentally Handicapped Children to Royal Mencap Society. It also has a new strapline: "Mencap, Understanding Learning Disability".
An internet marketing campaign has been launched to dispel myths about learning disability. The charity wants to encourage people to sign up to an "understanding charter" on its web site.
It also plans to reduce the use of colour in its promotional material and add factual information about learning disability.
Simon Cramp, a Mencap trustee, said: "We know that people don't understand what a learning disability is, what it means for that person or how they can help. We want to use the strengths of the Mencap brand to give people knowledge and encourage them to get involved."