An autopsy case of malignant schwannoma arising in the intracranial trigeminal nerve is reported. The tumor involved the right cerebellopontine angle of the brain stem in an 18-year-old man. The spindle-shaped tumor cells with eosinophilic cytoplasm proliferated in fascicles and exhibited hypercellularity, pleomorphism, increased mitotic activity and invasive growth. Ultrastructurally, interdigitating cytoplasmic processes and a few fragmented basal lamina-like structures were observed. Immunohistochemically, some tumor cells were reactive with conventional anti-S-100 protein antibody, but negative for beta subunit. Most tumor cells were positive for alpha subunit of S-100 protein. This is the eighth reported case of malignant schwannoma arising in the intracranial trigeminal nerve.