To the Editor: Surveys of neonatal diabetes in the UK and Germany from more than a decade ago reported an incidence of 1 in 400,000–450,000 live births [1, 2]. The permanent form of neonatal diabetes mellitus (PNDM) accounted for about half the cases, equating to a PNDM incidence of 1 in 800,000–900,000 live births. The definition of neonatal diabetes used in these publications was a diagnosis of diabetes within 4 weeks [1] or 6 weeks [2] of birth. HLA genotype analysis has shown that permanent diabetes diagnosed within the first 6 months of life is PNDM rather than type 1 diabetes [3]. Using a definition of diagnosis before 6 months, the incidence of PNDM was recently calculated at 1 in 214,000 live births from the Slovakian diabetes register [4]. We examined the incidence rates of PNDM in three further European countries. The incidence of neonatal diabetes for a country can be calculated from the referral rate of cases to a diagnostic laboratory and the annual birth rate, if all cases are referred to that laboratory. This will be less than the true incidence if not all cases are referred, but will still reflect a minimum incidence. In 2001 the Exeter Peninsula Molecular Genetics Laboratory based at the Royal Devon and Exeter Hospital (Exeter, UK) began recruiting patients worldwide prior to the discovery reported in 2004 that KCNJ11 mutations are the most common cause of PNDM [5]. The highest referral rates are in the UK, the Netherlands and Poland, where there have been considerable educational initiatives to inform clinicians of the free-of-charge diagnostic service