A metabolic study was made of 80 subjects of dementia praecox. Of these, half gave definite or presumptive evidences of endocrine gland deficiency. In 14 cases the thyroid gland was involved and in 13, the pituitary. In 13 others the specific gland at fault was not determined. Of the 80 patients, 53 received gland treatment. In the endo-crinopathic group half showed significant mental improvement. In the non-endocrine group only 5 instances of similar improvement were seen in 39 experiments. Following the gland treatment 5 patients became well enough to go home and treatment was suspended. One is continuing treatment at home and he, as well as 3 others still in the hospital, is nearly or completely free of psychotic manifestations. The highest incidence of improvement has been noted in the catatonic and the lowest in the paranoid group. This is possibly correlated with high incidence of thyroid deficiency in the catatonic, and of pituitary deficiency in the paranoid subjects. Of the gland substances employed, thyroid proved most efficacious. Mental improvement followed its use in 10 of 11 cases diagnosed as hypothyroid. In 11 non-endocrine cases none showed significant mental improvement following thyroid medication, though it served to correct certain physical conditions such as secondary anemia or reduced basal metabolism. The use of pituitary preparations by mouth was followed by improvement in 3 of 12 cases diagnosed as pituitary deficiency. It is probable that the dosages were inadequate. The gonad preparation used gave no significant evidences of efficacy. In only 3 of 37 "non-endocrine" cases were instances of significant mental improvement noted following the use of thyroid, pituitary or gonad substances alone. Two others improved on pluriglandu-lar therapy. The degree of improvement ultimately to be expected from the use of gland substances has not been determined nor can the permanency of such improvement as has occurred as yet be stated. It is concluded that endocrine deficiency plays a significant role in dementia praecox and that in properly selected cases specific endocrine therapy is of value in the treatment of this disorder.