The behaviour of blood sugar, insulin plasma free fatty acids and glycerol was studied at various times after intravenous glucose loading in patients with chronic renal insufficiency and normal subjects. Conard's K (glycide assimilation) coefficient was also determined. A statistically significant difference was observed between the two groups in the case of the K values only. No difference was noted in the case of the other parameters. The existence of two distinct groups within the subjects with chronic insufficiency, one with normal and one with altered K values, was also noted. The main physiopathological mechanisms probably responsible for this are discussed. It is considered that glucose loading is less sensitive i.v. than per os in the study of glycolipid metabolism in chronic renal insufficiency.