Rasmussen's encephalitis, a syndrome characteristically presenting in children with the onset of partial motor seizures followed by progressive hemiparesis and cognitive impairment, and accompanied by unilateral cerebral atrophy, was described nearly 50 years ago, yet the cause and optimum treatment remain unclear. Although it was originally presumed to have a viral aetiology, the possible roles of antibody‐mediated mechanisms and more recently cell‐mediated immunity in its pathogenesis have come under increasing scrutiny in the last ten years. These developments are discussed, together with a review of the clinical features. The advances in treatment which have accompanied these changes are also assessed.