The present chapter deals with the contribution of Professor Paul A. Bastenie, as Chief of the Department of Medicine of the Saint-Pierre Hospital and Director of the Laboratory of Experimental Medicine at Brussels Free University, in the field of diabetes with emphasis on the role of insulin in glucose homeostasis. The knowledge and experimental work under consideration is covering the period from 1955 to 1974. They entail not only three treatises contributed by Bastenie but also fundamental and clinical investigations, such as those presented in eight doctoral dissertations submitted for aggregation examination at Brussels Free University. These theses are dealing with the measurement of glucose assimilation (V. Conard), the measurement of insulin activity in men (J.R.M. Franckson), the mechanisms of action of hypoglycemic drugs (R. Bellens), the study of energy metabolism in children (H. Loeb), the study of insulin secretion in vitro (W. Malaisse), the distribution of insulin in body fluids as influenced by the permeability and structure of blood capillaries (E. Rasio), the regulation of the extra-hepatic metabolism of ketone bodies in anesthetized dogs (E.O. Balasse) and the use of radioiodinated insulin as tracers in biology (H.A. Ooms).