There is evidence that the Pena-Shokeir syndrome is not a specific phenotype but should be regarded as a "fetal akinesia deformation sequence". A neuropathological study of six random new cases was performed to evaluate this theory. Brain pathology observed included persistent fetal meningeal vascularization (two cases), agenesis of the septum pellucidum (one case) and hydranencephaly (one case). Investigation of the spinal cord (in two cases) revealed no abnormalities. Muscle histology (in four cases) was indicative of neurogenic atrophy in two cases. These findings are compared with the data of the 28 cases previously described. It is concluded that the Pena-Shokeir syndrome is a heterogeneous syndrome in which cerebral lesions may play an important role in the pathogenesis. The cerebral malformations may also indicate the time of origin and contribute in the perinatal death of this syndrome.