Our first hypophysectomy in a metastatic carcinoma of the breast was performed in November 1951 and the section of the pituitary stalk (mischotomy) for the same purpose was started in November 1955, the first results being published in 1956. When one succeeds in preventing the hypothalamohypophyseal vascular regeneration the general results of mischotomy are little different from those obtained with hypophysectomy. We adopt mischotomy when total pituitary removal seems to be a too great surgical risk. Anatomo-physiological studies are being published since 1958, showing: (a) The variations of the anterior lobe necrosis which is neither total nor definite (pituitary regeneration) and the importance of the trabecular arteries in that respect; (b) The striking ability of vascular regeneration from the hypothalamus to the anterior lobe remnants thus creating a new anatomical and functional portal system; (c) After permanent pituitary isolation, the proliferation of prolactin (orangeophile) cells and the compensatory hypertrophy of pars tuberalis. Removal of normal pituitary tissue obtained during the operation allowed us to describe for the first time in man the ACTH cells (1964) and the FSH cells (1966).