We report the clinical records of 45 children with abnormalities regarding glycemic regulation characterized by a non-insulin deficient hyperglycemia (NIDH), known under the different names of chemical diabetes, sub-clinical diabetes and more recently MODY. These 45 children belong to 31 families with 532 relatives comprising 137 cases of NIDH which could have been studied. The symptoms of this biochemical abnormality, the pathophysiology of which is not yet clearly understood, are the following: lack of clinical manifestations, except for a variable and intermittent glycosuria; constant abnormal glucose tolerance tests, above 97 percentiles of the reference value with some variations over time; normal immunoreactive insulin levels; percentage of glycosylated hemoglobin at the upper range of normal; dominant autosomal genetic transmission and no association with HLA markers like in insulin-dependent diabetes; lack of degenerative complications of the micro-angiopathic type, at least on these cases even after more than 30 years of follow-up; finally, no tendency towards insulin-dependent diabetes. The NIDH should not be confused with the slow and progressive beginning of insulin-dependent diabetes for which prolonged delay is needed to affirm the diagnosis. The frequency of the biochemical phenomena is about 1.8% of the cases of authentic diabetes mellitus occurring before the age of 15.