Eligibility All patients with a physician-confirmed diagnosis of diabetes and who have been followed in the diabetes centre for at least one year are eligible Sample size In order to detect a difference of 1 unit (1% glycated haemoglobin) between to samples with a standard deviation of 1.2%, alpha coefficient of 0.001 and 0.8 power using a two-sided test, a minimum population of 80 subjects is required. The minimum sample size if alpha is 0.01 is 55 subjects. We therefore decided a sample size of 100 patients per centre in order to be able to analyze data taking into account center or physician effect. It thus give an overall sample size of 1000 subjects.