In the medical literature there are up to the present no data available concerning the excision of primary tumors of the basal ganglia. We wish to record our experience with radical excision of some of these tumors, which was performed because palliative operations (decompressions) did not yield satisfactory results. Pathological Anatomy Primary tumors of the basal ganglia may have their starting point in the thalamus, the nucleus caudatus, or the nucleus lenticularis. Those starting in the thalamus are the most frequent. Thalamic tumors are mostly intrinsic tumors of neuroglial origin. They are likely to arise in any part of the thalamus, but usually they appear to have had origin in the subependymal layer of neuroglia. There is a relation between the structure of the subependymal layer of the third ventricle and that of the tumors which occur in this area and invade the basal ganglia (Opalsky). The subependymal layer of