The positron-emission tomography (PET) findings in a seven year old girl with the juvenile form of Huntington's disease are described from the Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, Montreal, Canada. The birth and early development were normal and at three years of age she could dance and ice skate. By 3£ years she had difficulties in dancing and by four to five years of age she had developed an awkward stiff gait, she became socially withdrawn in personality, had frequent nightmares, speech was dysarthric, and she began to fall frequently and to have problems controlling her hands. Swallowing, chewing and speech progressively deteriorated. She was hypertonic and had exaggerated deep tendon reflexes. Her father had Huntington disease. Her EEG showed bilateral epileptic foci but she had no clinical seizures. PET showed marked reduction in cerebral glucose metabolism in the posterior nuclei of the thalamus, a finding that differs from adults with the disease who show normal or increased rates of thalamic glucose metabolism. These metabolic findings were consistent with previously recognized postmortem pathologic differences between juvenile and adult forms of the disease. [1]