We report a case of anorectal melanoma, whose first manifestation was a carcinomatous meningitis. The anorectal melanoma is a rare tumor of great malignity which represents 1-3 per cent of melanomas and 0.5 per cent of anorectal tumors. The most frequent symptoms are non-specific: rectal bleeding, pain at defecation, changes in the intestinal rythm. Sixty per cent of cases presented metastasis at the moment of diagnosis limited to the regional lymph nodes. In none of the cases published did the metastasis present as the first symptom. The case presented here manifested itself only with neurologic symptomatology compatible with carcinomatous meningitis whose finding led to the search of the original tumor, and this is what makes this case exceptional since the infrequency of this tumor is united to an unusual clinical presentation, not previously described in the literature.