Malignant peripheral nerve sheath tumor (MPNST) is an uncommon sarcoma in the pediatric population; however, its presence should be considered in a child with an enlarging or painful soft-tissue mass. Diagnosis of this neoplasm depends on either the demonstration of its origin within a peripheral nerve or the association with a contiguous neurofibroma. We have identified 16 cases of MPNST involving children 16 years of age or less, which represent 12.8% of the total cases seen at the Mayo Clinic. Most of the lesions arose in children with von Recklinghausen's disease and were associated with a contiguous neurofibromatous component. The mean survival of patients who were known to have died of tumor was only 1.8 years. This sarcoma requires prompt aggressive therapy utilizing wide surgical excision. Because of the association of MPNST with von Recklinghausen's neurofibromatosis, a careful workup and family history should be obtained for the potential prognostic value and for the purpose of genetic counseling.