Both the treatment pattern and the degree of metabolic control were estimated from a sample of 1172 French diabetic patients. The subjects were recruited from 80 medical-analysis laboratories scattered throughout the country, where they came for biologic blood sample tests. Patients had to be diagnosed as having diabetes, give consent for additional blood sampling, and fill out a short self-questionnaire. Glycosylated hemoglobin A1c (HbA1c) was centrally determined by liquid chromatography (normal range 3.5–6.3%). We found 135 patients (11.5%) who were not drug treated or treated with diet alone, 862 (73.5%) treated with oral agents, and 175 (15.0%) treated with insulin. Among the latter, 79 (6.7%) were defined as true insulin-dependent diabetes mellitus (IDDM) patients. Among patients receiving no drug or a slight dosage of oral agents, 47% were found to be in the normal range of HbA1c. On the other hand, among the patients intensively treated with oral agents or secondarily with insulin, less than half were under fair control (HbA1c 1c values in non-insulin-dependent diabetic patients suggests a state of overdiagnosis linked to the use of nonspecific criteria of diagnosis in large-scale screening.