A woman aged 36, who two years previously had undergone a caesarean section, developed a painful swelling of the scar attributed to cicatricial endometriosis. This is a rare disorder brought about by peroperative displacement of normally or ectopically situated uterine mucous membrane to the surgical wound. There, it may proliferate and cause characteristic signs and symptoms that are simple to diagnose: cyclic pain, swellings and sometimes, bleedings. Pharmaceutical, possible hormonal treatment is of limited value, because cessation of the medication is frequently followed by recurrences. Consequently, ample surgical excision in endometriosis is to be preferred; this is to be regarded as a curative therapy.