Eight adult patients with malignant peripheral nerve sheath tumors of the orbit are described. Only two of the patients were known to have von Recklinghausen's neurofibromatosis. The typical clinical history included the development of a mass in the superonasal quadrant of the orbit, which was palpable immediately beneath the skin of the lid. There was a definite tendency for the lesions to arise in, or grow along, the supraorbital nerve--including posteriorly through the superior orbital fissure to the Gasserian ganglion, and even as far posteriorly along the trigeminal rootlets to the pons. Delays in pathologic diagnosis, which beclouded the true nature of the process, led to multiple recurrences, eventuating in five known fatalities out of the eight patients. In addition to intracranial extension, pulmonary metastases and regional cervical metastases were encountered. Once recognized for their diagnostic value, the histopathologic patterns are highly distinctive: biphasic populations of spindled and epithelioid cells; sheets of epithelioid cells or clusters demarcated by delicate reticulin fibers or thicker collagenous trabeculae; malignant plexiform patterns; and neurotubular patterns. Pure spindle cell populations were encountered only in the two patients with von Recklinghausen's disease, and in each, either a pre-existent benign neurofibroma or a coexistent plexiform neurofibroma was found in the pathology specimens. The best management of this condition depends upon early clinical and pathological recognition, leading to radical surgery, which usually consists of orbital exenteration combined with intracranial extirpation of as much of the trigeminal nerve as possible. Postoperative radiotherapy and chemotherapy after radical surgery might also be advisable.