Pituitary adenomas, either chromophobe or chromophile, are a relatively frequent type of intracranial growth. In our total series of 1963 brain tumors seen at the Lahey Clinic through the year 1955, there were 335 adenomas, representing 17% of all tumors. Of this number, 141 were verified pathologically (1 by necropsy, the other 140 surgically), whereas in the case of the remaining 194 the diagnosis was made without any reasonable doubt by the finding of a greatly enlarged sella turcica by roentgenogram, together with optic nerve atrophy, visual field changes, or other characteristic pituitary stigmata, such as acromegaly. In the early days of this century the only known treatment capable of reducing the size of pituitary adenoma, thus relieving pressure on the optic nerves with restoration of vision, was the operative removal of varying amounts of the growth. This was accomplished for many years by the so-called transsphenoidal procedure, with reasonably