Primary malignant melanoma of the anorectum is a rare and virulent malignancy associated with an extremely poor prognosis in spite of aggressive initial therapy. Fifty‐one patients with this disease were treated at Memorial Sloan‐Kettering Cancer Center during the last 50 years and only six (12%) survived five years. This report views in detail 36 of the patients treated since 1950. In this group there was a female predominance (21 females, 15 males), and median age was in the 6th decade (range 27–75). Common presenting symptoms were pain, bleeding, mass or “hemorrhoids” of 1‐12 months duration. In two‐thirds, of the cases, a radical surgical approach was attempted. Other therapy included local excision alone or combined with groin dissection, local excision followed by delayed rectal resection and local tumor destruction by cryosurgery or fulguration. Mean survival was 21.5 months. Three patients had palliative treatment only with radiation therapy. Histopathologic study of 30 lesions showed that two‐thirds were bulky or polypoid lesions and two‐thirds showed junctional changes. The virulent prognosis of primary anorectal melanoma appears directly related to tumor size and thickness. Although all four of the five‐year survivors had radical surgery, the three whose tumors could be measured had superficial lesions. In general, curative efforts by radical surgery were no more effective than local treatment by excision or cryosurgery. One patient, however, did have a thin lesion but also had nodal metastases and survived over five years after radical surgery. Although these data suggest that radical resection may cure patients with lesions thinner than 3 mm, it does not exclude the possibility that local excision might also be curative. For larger lesions that have not been cured by radical surgery, more conservative local approaches by excision or cryotherapy might be the optimum way of achieving local palliation.