THE TRANSITION of hernia of the esophageal hiatus, more commonly called hiatus hernia, from a rare entity to one of comparative frequency has taken place in the past two decades. It was some years after the advent of diagnostic roentgenology that appreciation of the diagnostic value of changes in position of patients during barium study of the gastrointestinal tract led to routine study of the patient in the prone, supine or Trendelenburg positions. Ritvo1 in 1930 emphasized the importance of this maneuver in bringing to light many previously undiagnosed hiatal hernias, particularly of the recurrent, small variety which may be seen only in the Trendelenburg position and may, indeed, be absent at another examination. Jenkinson and Roberts2 estimated that only 5 per cent of hiatus hernias could be diagnosed if the erect position alone were used during examination. Since the radiologist has attained a high degree of awareness