A 43-year-old woman who had a vulvar mass associated with mild discomfort was found to have a rare primary vulvar adenocarcinoma of probable cloacal origin. The tumor was contiguous with the surface epithelium of the vulva and was a well to moderately differentiated adenocarcinoma of colonic type. Stains of the neoplastic cells were positive for both acid and neutral mucin, and periodic acid-Schiff (PAS) was positive after diastase reaction. The neoplastic cells were strongly positive for carcinoembryonic antigen, broad spectrum cytokeratin, and p-53 antigen. Clinical evaluation failed to show any primary tumor in colon, lung, or breast. The patient was disease free 18 months after operation.