The following case of pituitary tumor illustrates what is already so well known, namely, that the pituitary gland influences the sex development of the individual. This case illustrates how certain types of pituitary tumor may produce an inversion of the sex characteristics. The patient, a man of 52 years of age, referred by Dr. L. Adler, was admitted to Harper Hospital on May 21st, 1929, with a history that for about a year he had had vertigo and headache in the frontal region and impotency for the last two years. He had noticed that during the past two years his breasts were increasing in size and were taking on so-called female characteristics. Vertigo had increased over the period of the last year and in the last month previous to admission it had become very much worse. The headaches likewise increased. There was no complaint about vision. Four weeks prior to admission he began to notice a gradual loss of the use of the right arm and drooping of the right corner of the mouth. His speech became so muc...