Infantile olivopontocerebellar atrophies are rare progressive, fatal, neurologic conditions characterized pathologically by loss of neurons and gliosis in the cerebellum, pons, and inferior olivary nuclei in early life. The clinical and pathologic features of 2 brothers who presented in early infancy with failure to thrive and neurologic deterioration leading to death by the age of 5 months are reported. Magnetic resonance imaging of the brain of Patient 1 disclosed progressive pontocerebellar atrophy. Both siblings had identical patterns of neuronal loss consistent with olivopontocerebellar atrophy at postmortem examination. Serum biochemical abnormalities of low thyroid binding globulin, hypoalbuminemia, and low cholesterol, suggestive of the carbohydrate-deficient glycoprotein syndrome, were also present in both patients.