Human growth hormone (HGH) has recently been shown to play a prominent role in the control of blood glucose homeostasis. Furthermore, it has long been known that administration of growth hormone in animals can induce a diabetes-like state. In human subjects, exogenous administration of HGH or hypersecretion of the endogenous hormone in acromegaly is accompanied by glucose intolerance in only about 25 per cent of the cases. — In this paper, data are presented which give a more diversified picture of the so-called diabetogenic action of HGH. It is suggested that HGH, although decreasing the peripheral utilization of glucose, is not a primary diabetogenic factor, since its insulinogenic action causes a compensatory hyperinsulinism, with normal glucose tolerance as the result. HGH is diabetogenic only in prediabetic subjects whose pancreas is unable to respond to the insulinogenic effect of the hormone. In such subjects, the diabetogenic action of HGH not being counterbalanced by a compensatory hyperinsulinism, glucose intolerance may result. Thus, HGH may be regarded as anadditional factor for the development of diabetes, the major prerequisite being a preexisting prediabetic state.