Neonatal hydrometrocolpos is a rare congenital disorder consisting of cystic dilatation of the vagina and uterus resulting from imperforate hymen or vaginal atresia. We report 3 cases of vaginal atresia, case with hydrometrocolpos associated with polydactyly and 2 cases combined with persistent urogenital sinus and imperforated anus. In each case, a sonograph showed a characteristic cystic abdominal mass containing a fluid/debris shadow with an interphase.