Problems of diagnosis, classification, and histologic definition, as well as possibilities of evolution are discussed, of teratomas or of tumours resulting from the disturbed development of the sacro-coccygeal area, in connection with a case of recidivating sacro-coccygeal teratoma in a woman aged 40 years. The therapeutic principles are also discussed The risk of malignant degeneration of these lesions, in parallel with their evolution in time, make necessary surgical exeresis immediately after making the diagnosis. Surgery should be performed with a maximum amount of comfort, under general anesthesia, preferably in the Kraske position, in view of the complete extirpation of pathological tissues. Resection of the coccyx and of the last sacral vertebrae allows to widen the approach, facilitating the complete exeresis, and avoiding the two risks which are characteristic for this intervention: lesion of the rectum, and haemorrhage which is difficult to control. The postoperative aspiratory draining is useful for the favourable evolution of the wound.