The clinical and pathologic features of a malignant extragastrointestinal stromal tumor presenting as a vaginal mass are discussed. A 66-year-old female presented with copious vaginal bleeding and spontaneous passage of tumoral tissue per vagina. Histologic assessment showed a mitotically active spindle cell neoplasm. Immunohistochemical analysis demonstrated the neoplasm to be positive for CD117 (transmembrane tyrosine kinase) and CD34, consistent with a malignant extragastrointestinal stromal tumor. Subsequent clinical examination revealed an 8-cm posterior vaginal wall mass, with probable origin from the rectovaginal septum. This case is unique based on the primacy of presenting gynecologic complaints, and the unusual anatomic location of the lesion. A literature review of the pathologic features of extragastrointestinal stromal tumors and factors predictive of biologic behavior are discussed. Correct tumor diagnosis is emphasized given the effective treatment possible with imatinib for patients with unresectable tumors.