An imperforate hymen is a congenital anomaly caused by a failure of the hymen to perforate during fetal development leading to complete obstruction of the vagina. An imperforate hymen is most often diagnosed in adolescent girls after the age of menarche with otherwise normal genital development. An imperforate hymen can also be diagnosed in newborn babies. This chapter discuss the embryology, clinical features, diagnosis and treatment of imperforated hymen.