Leigh's disease, also known as subacute necrotizing encephalomyelopathy, is a rare progressive neurological disorder of childhood that was first described by Leigh in 1951. Diagnosis of this disease can be difficult because onset is usually insidious and can present with a number of different focal findings, however diagnostic imaging has been shown to be of benefit in this regard. We present a patient with Leigh's disease in whom serial MR imaging studies helped to make the diagnosis and also demonstrated the dynamic characteristic of this disease process.