The roentgenologic examination of the pelvis in a material of parae as well as nulliparae and men is discussed. During pregnancy a degree of vertical stretching of the symphysis pubis was shown to occur; it was reduced post partum but never entirely disappeared. In parae sclerosis or subsclerosis in the region of the sacro-iliac joints was also demonstrated; these changes were rarely found in nulliparae or men. It may thus be determined at any time with only a slight chance of error whether or not a woman has ever had a pregnancy. Measurements of the static sacral angle showed that parae with an angle of over 55° developed pregnancy pain, while parae with an angle of 55° or less remained free.The importance of the musculature in the pathogenesis of pregnancy pain is discussed and the conclusion drawn that women with a static sacral angle of over 55° should make an effort to maintain the abdominal musculature during pregnancy. Measurement of the static angle may also be of importance in establishing the diagnosis in cases of inexplicable low lumbar pain.