We report three siblings (two boys and girl) with familial (autosomal recessive) infantile olivopontocerebellar atrophy (OPCA) associated with lower motoneuron involvement. Brain autopsy findings in two of the children revealed a multisystem degeneration characterized by marked hypoplasia of phylogenetically new parts of the brain stem (basis pontis and inferior olivary nuclei) associated with hypoplasia of the neocerebellum, both cerebellar and cerebral peduncle. All three infants died before six months of age. The clinical features are characterized by severe hypotonia, areflexia, failure to thrive, respiratory insufficiency in all cases, cardiomyopathy and dislocated hips at birth in two of the three siblings. Extensive serum, urinary and leukocyte enzyme assays in the second infant failed to disclose a specific metabolic abnormality. The diagnosis of OPCA was established prior to death by Magnetic Resonance Imaging (MRI) in the youngest infant. Since OPCA represents a heterogeneous group of diseases, correlation of neuropathologic, clinical, genetic and MRI findings at early stages of evolution becomes crucial in the understanding of the nosology of OPCA and its variants.