✓ The pituitary remnant was examined in 13 patients in whom a stereotaxic, transsphenoidal, high-frequency coagulation had been performed because of widespread metastatic disease. The patients were divided in three groups according to the state of regeneration of pituitary tissue. The first group (patients dying 3 to 7 days after surgery) showed only signs of acute necrosis. The second group (patients dying 24 to 219 days after surgery) demonstrated mitotic figures and regenerated areas in the adenohypophysis. The third group (patients dying 252 to 353 days after surgery) showed no mitoses but large areas of regenerated glandular cells as a sign of completed regeneration. It seems that the pituitary can regenerate provided that the dominating hypothalamic centers remain undamaged during hypophysectomy.