Alexander 'Dr Xand' van Tulleken and Christoffer 'Dr Chris' van Tulleken (born 18 August 1978) are British doctors, TV presenters and identical twin brothers.
They are best known for presenting the series Operation Ouch!.
Chris has become well known for his two-part television special for BBC One entitled The Doctor Who Gave Up Drugs.
Xand has also presented shows without his brother.