SummaryOn admission in diabetic keto acidosis (glycemia 350 mg/100 ml, alkali reserve 4,4 mEq/L), a young non obese soldier was found to have an important hyperlipemia : lactescence of the plasma, triglycerides 23,600 mg/100 ml, cholesterol 1,020 mg/100 ml, phospholipides 1,500 mg/100 ml. The diabetes was unrecognized despite typical symptoms since three months.After prompt rehydratation and insulinotherapy, all lipid fractions of the blood returned to normal along with a good equilibration of the diabetes and a normal diet : total lipids 1,000 mg/100 ml on 15th day and 600 mg/100 ml at the end of the second month.Six months after this episode, the plasma lipids were normal and the diabetes well controlled, with 50 U insulin a day. The patient was then carefully studied in a metalwlic ward during a two month period : the insulin was purposely reduced to 15 U a day and two isocaloric (2,000 G) diets were successively followed : a first one with 162 g fat and 52 g carbohydrate and a second one with 45 g fat and 422 carbohydrate. The diabetes was then poorly controlled but no ketosis developed. All lipid fractions remained practically normal.It is concluded that this hyperlipemia was of true«diabetic»nature, reflecting a deep but progressive insulin lack, developing in an otherwise constitutionally normal subject.