An infant with Leigh disease, who was the younger sister of a similarly affected infant, had been examined before the onset of the disease. Ultrasonography revealed hyperechoic lesions in the putamen and caudate nucleus during the preclinical stage. At onset, these changes extended into the cerebral cortex and medulla. These lesions were also detected by T2-weighted magnetic resonance imaging (MRI) as areas of increased signal intensity. Her brother demonstrated the same ultrasonographic results; cranial computed tomography disclosed low-density areas in the basal ganglia which were detected as hyperechoic lesions by ultrasonography. These findings suggest that ultrasonography is useful in detecting early intracranial lesions in Leigh disease.