In 6 type 1 (insulin-dependent) diabetics, treated with insulin since the age of 2 to 35 years (mean 12), coeliac disease was diagnosed between the 10 th and 73 th years of age (mean 26). Five were of North African origin. Digestive symptoms and severe malnutrition were present in all of them, associated, in the two younger, with a major growth retardation and, in one, multiple pathologic fractures. Biopsy of the small intestine demonstrated, in all, total or subtotal villous atrophy. The metabolic control of diabetes was poor, with frequent hypoglycaemic attacks, induced by minute insulin doses. Severe chronic complications of diabetes were detectable in all of them. Plasma anti-reticulin antibodies were present, at high titer before starting the gluten-free diet, declining slowly after starting this diet, and negative in the patients who followed this diet. Among the genetic markers (which were determined in 4), HLA A1 was present in 4, B8 and DR3 in 3 and DR4 in 3. The DR7 was not detected. The gluten-free diet, memorized by the patients by the use of simple rules, improved the digestive symptoms, and insulin doses could then be increased. The overall prognosis remained poor, due to diabetic complications and sociologic desinsertion. Coeliac disease occurs in 1 to 2% of type 1 diabetics and 4-6% of the coeliac patients are diabetics. Diabetic subjects from North Africa are at high risk of this association. Misdiagnosis of the coeliac disease compromises the metabolic control and nutritional state.(ABSTRACT TRUNCATED AT 250 WORDS)