A series of 18 primitive neuroectodermal tumors in children (15 cerebral and three spinal) is reported. These are highly malignant neoplasms, both histologically and clinically. They are rapidly growing tumors, with a brief duration of symptoms and a rapidly progressive course. Forty percent of the patients were alive at 6 months, only 10% at 1 year, and all patients had died within 2 years following diagnosis.