• Insulin tolerance tests (ITTs) were carried out on 46 drugfree prepubertal children with severe emotional disorders. Thirteen met unmodified Research Diagnostic Criteria for major depressive disorder, definite endogenous subtype, 17 met the criteria for nonendogenous major depressive disorder, and 16 fit DSM-III criteria for nondepressed neurotic disorders. The group with endogenous depression had significant hyposecretion of growth hormone (GH) in this test when compared with the other groups. Since GH hyposecretion in response to ITT has been found in most studies to be associated with endogenous major depression in adults, the data support the validity of the diagnosis of prepubertal endogenous major depressive disorder and the hypothesis of similarity or identity of prepubertal and adult major depressive disorders.