Although nearly 600 articles concerning pituitary adenomas and craniopharyngiomas have been listed in the Quarterly Cumulative Index Medicus since its first volume, in 1916, only 13 are primarily concerned with the psychological changes which these lesions may produce if they expand upward to an unusual size. We have been able to find incidental brief allusions to this complication in a few others. Harvey Cushing1 barely mentioned the possibility in his series of 360 pituitary adenomas; but, in a subsequent follow-up of these patients, Henderson2 found 51 who suffered from mental deterioration, hallucinations, or somnolence in the later stages of the disease. Olivecrona, of Stockholm, who has had the most extensive modern experience with this condition, and Bakay,3 who has reviewed his material, mention mental symptoms in only a single patient with a recurrent tumor. According to Bakay (personal communciation), this patient is now severely deteriorated in a