We describe herein the clinical symptoms, clinical course and results of investigation of 7 patients with bilateral basal ganglia-thalamic lesions (BBTL). All patients had spastic quadriplegia with rigidity. They were unable to sit and turn over. They could follow objects, turn head towards a sound and recognize parents to some degree. They were all evaluated as having the most severe degree of disability (Oshima's classification 1). They all had dysphagia and 2 patients had a episode of bradycardia and hypothermia, which might be evidences of brain stem disorders. Muscle hypertonia, vomiting, hematemesis and obstructive respiration, which were the major complications for the patients, worsened with age. High percentage of histories of birth asphyxia and poor feeding in the neonatal period suggested that perinatal brain insults might be one of the important factors for developing BBTL. It seemed to be difficult to explain that such diffuse brain injuries in our cases were caused by only the insults during parturition. Brain insults during parturition as well as prenatal factors probably participate in developing BBTL. Although the cerebrum of the patients seem to be relatively preserved in the images of head CT-scan, MRI of the patients revealed diffuse brain lesions. All of five patients tested had an abnormal auditory brain stem response (ABR). These investigations demonstrated that patients with BBTL have diffuse brain damage including brain stem. Further observation is needed to verify the mechanisms of development and the time of onset of BBTL.