Since Deanesly & Parkes [1937, 1938] first introduced the technique of subcutaneous implantation of tablets of compressed crystals of sex hormones in animals, further experiments have been conducted by those workers and by many others in different parts of the world. This method gives a continuous small absorption, simulating the normal secretion of the gonads, except that the amount absorbed is in no way controlled by any such normal factors as tissue requirements or pituitary stimuli. Clinicians were not slow to adopt this new technique, and Bishop [1938] reported the implantation of a 14 mg. tablet of oestrone into a menopausal woman, which relieved her symptoms for about 4 weeks, after which the effect began to wane. I [Foss, 1939] reported the results of such therapy in fifteen patients suffering from kraurosis, pruritus and leukoplakia and found that, with the doses used, relief was not obtained by this means alone.