The embryology of the genital tract and urinary system is described, and the hypothesis is advanced that the vagina is an organ embryologically derived from the mesonephric or Wolffian ducts in addition to the Müllerian tubercle. This is based on experimental studies and case reports in the literature and our own cases of genital malformations, especially in patients with unilateral renal agenesis and an ipsilateral blind vagina. The importance of the mesonephric ducts as guides or ‘inductor’ elements for adequate Miillerian development is emphasized. A new embryological classification of female genital malformations is proposed, based on these embryological concepts.