The authors report 11 cases of sacro-coxitis due to pyogenic bacteria observed over a period of seven years and emphasize that this is a disease of young women recently in labour, usually due to staphylococci which enter through the genital tract. The other methods of contamination are urinary, cutaneous and dental. The onset is usually acute, pseudoembolic and bacteremia. Whereas the diagnosis is purely clinical as X ray remains normal until the 15th or 20th day, all steps should be taken to identify the germ. With antibiotics, a cure is obtained without sequelae within 3 months. Surgery is only justified if tuberculosis is suspected and in exceptional cases with abscess formation.