The biological vagaries of anal malignant melanoma are illustrated by four cases in Chinese patients. All four died within five years. Their poor prognosis emphasizes the value of preoperative studies to detect clinically occult metastases and obviate futile radical surgery. Many patients already have disseminated disease at the time of diagnosis, and local excision of the tumour provides acceptable palliation. For localized disease, abdominoperineal resection prevents local recurrence and removes the mesenteric nodes which are frequently involved. Palpable inguinal nodes necessitate therapeutic groin dissection, but we perform elective resection only when affected nodes are found at laparotomy. Pelvic lymphadenectomy should be performed in conjunction with abdominoperineal resection. The efficacy of chemotherapy for anorectal melanoma remains uncertain.