Background As one of the rare types of melanoma,anorectal melanoma (AM) accounts for 0.4%-1.6% of total malignant melanomas.However, its incidence increased with time and it remains a highly lethal disease, with 5-year survival rate at 6%-22%.Due to its rare nature, most of the literature about AM was isolated ease reports and derived from single-center series,which couldn't give comprehensive assessments of this disease.Therefore,we conducted this population-based study based on Surveillance, Epideniology,and End Results (SEER) program,to provide the latest and best available evidence of AM.Methods We extracted all cases of AM registered in the SEER database from 1973 to 2011 (April 2014 release) and calcutated the age-adjusted incidence.Then,only cases with active follow-up were included to predict factors associated with prognosis.We also compared survival outcomes between different types of surgery.Results We identified 640 cases of AM, comprising 265 rectal melanoma and 375 anal melanoma.The crude annual incidence per 1 million population of AM was 0.259 in males and 0.407 in females, which increased with advancing age and time.As expected,tumor stage and surgical treatment were found to be independent predictors of survival.And our results implyed that patients of local or regional stage could achieve prognostic benefits from surgery,while surgerical treatment couldn't prolong survivial in distant-staged patients.Furthermore, no statistical difference was observed comparing less extensive excision(LEE) with more extensive excision(MEE).Conclusions This study provides an up-to-date estimation of the incidence and prognosis of AM on the basis of SEER data.AM is uncommon but its incidence increased with time and it had a poor grognosis,which requires our growing concern about this disease.Refering to surgical treatment of disease, wc advised LEE for local and regional staged patients,for less complications and better prognosis.