Gynecologic affections have been variously estimated to be the cause of lumbo-sacral backache in women in from 30 to 85 per cent of cases. Recently, however, more exact knowledge has greatly reduced the relative importance of the so-called gynecologic backache. In my own experience, the gynecologic causes of backache have been greatly overestimated. There are three great groups of backaches occurring in women; namely, I the pelvic type, which may result from a physiologic congestion at the menstrual epoch or uterine malpositions and pelvic inflammation; 2 the orthopedic type, arising from such conditions as sacroiliac relaxation, faulty posture, flat feet, spondylitis, and involvement of the lumbar muscles or fascia; and 3 the focal infective type, due to distant infection in the teeth, tonsils, accessory nasal sinuses, or elsewhere. Every case of obscure backache requires a study of the entire patient. Only when the investigation is conducted carefully from all angles may we hope to discover the particular cause in an individual case and thus be in a position to direct effective treatment.