Abstract： Serous adenocarcinoma of the vaginal-urethral interspance with unknown origin has not previously been reported.Based on existing evidence,serous adenocarcinoma was considered to be a mesonephric adenocarcinoma.Mesonephric adenocarcinoma is a rare tumor of the female genital tract derived from mesonephric duct remnants or hyperplasia.Among the small number of reported cases,most are related to the uterus and cervix.There is no literature pertaining to optimal therapy,and little is known about the response to chemotherapeutic agents and prognosis.Here,we reported a case of a mesonephric adenocarcinoma of the vaginal-urethral interspace in a 43-year-old woman with 4 years of follow-up.