Two cases are presented of a partially duplicated vagina characterized by a one-sided hematocolpos associated with renal agenesis on the same side. A review of the English literature reveals 39 previously reported cases. Invariably this complex of anomalies is seen in adolescents and young women with progressively severe abdominal pain, menstrual irregularities, and a pelvic mass. It is important to make an early accurate diagnosis since they are usually managed as having an ovarian mass and submitted to multiple laparotomies and occasionally to mutilating surgery. An analysis is presented of the salient embryologic, clinical, and radiologic features of the 41 cases gathered. The need for definitive preoperative evaluation of both the urinary tract (urography and cystoscopy) and the genital tract (hysterosalpingography) cannot be overemphasized.