Total pancreactectomy in the dog is followed by an increase in lipemia and ketonemia. Insulin either prevents or corrects these metabolic disorders. Lipemic and ketonemic augmentation is due to two factors: (a) lack of insulin; (b) simultaneous presence of the pituitary and adrenals (or their hormones). Hypophysectomy or adrenalectomy prevent or attenuate significantly hyperlipemia and ketoacidosis. Somatotropin increases ketonemia in the early pancreatectomized-hypophysectomized dog (with adrenals) and has no ketogenic action in the pancreatectomized-adrenalectomized and pancreatectomized-hypophysectomized-adren-alectomized dogs (without adrenals). Therefore the pituitary is necessary for the development of ketoacidosis in presence of adrenal glands (or their hormones). Cortisol administration is followed by hyper ketonemia in the pancreatectomized-adrenalectomized dogs (with pituitary) but it has no ketogenic action in the pancreatectomized-hypophysectomized and pancreatectomized-hypophysectomized-adrenalectomized dogs (without pituitary). Cortisol ketogenic action does not occur in the absence of the hypophysis (or somatotropin). The combined administration of hypophyseal and adrenal hormones increases the ketonemic level, reaching that of the pancreatectomized dogs without insulin. This effect of the hormonal association is observed in the pancreatectomized dogs deprived of the pituitary or the adrenals or both glands whose hyperketonemia following insulin withdrawal is depressed. The hyperlipemia of the pancreatectomized dogs deprived of insulin is due to lack of insulin and simultaneous presence of hypophysis and adrenals (or their hormones). Hypophysectomy or adrenalectomy prevent or attenuate clearly the hyperlipemia of the pancreatectomized dog deprived of insulin. Somatotropin induces marked hyperlipemia in the pancreatectomized-hypophysectomized dogs with adrenals, but has no hyperlipemic effect in the pancreatectomized-adrenalectomized dog without adrenals. The adrenal glands are necessary for the hyperlipemic action of somatotropin to take place. Cortisol administration is followed by a definite increase in lipemia in the pancreatectomized-hypophysectomized dog or the pancreatectomized-adrenalectomized dog and by a lesser one in the pancreatectomized-hypophysecromized-adrenalectomized dog. Thereof it mobilizes lipids in the absence of pituitary, adrenals or both glands. Diabetic hyperlipemia is observed only in the presence of adrenal glands or their hormones. Somatotropin enhances the hyperlipemic action of cortisol. Cortisol actually increases the lipemia but not the ketonemia in the absence of hypophysis. Usually hyperlipemia precedes hyperketonemia. In the pancreatectomized-hypophysectomized dogs, somatotropin action diminishes gradually after hypophysectomy, and is minimal or negligible from the thirtieth to the eightieth day after hypophysectomy.