PRIMARY malignant melanoma of the central nervous system is a relatively rare neoplasm. Such a growth arising in the spinal cord is even more unusual. When one is encountered, it is often difficult to tell whether the lesion is secondary to a melanoma elsewhere in the body or whether it has spread from one in some other part of the central nervous system. Since many melanomas are not diagnosed until necropsy, it is sometimes difficult to ascertain just the point within the central nervous system from which the neoplasm arose, since the tumor frequently spreads throughout the subarachnoid space either by direct extension or by "seeding." Sometimes dense and extensive metastases occur throughout the leptomeninges, which have been described as "tumor meningitis." It was Virchow1 who in 1859 first reported a case of primary melanoma sarcomatosis. Since that time occasional reports in the literature have appeared, but the number