Diabetes is one of the most common paediatric chronic diseases. Type 1 diabetes is the leading form of diabetes in young white people, especially those of northern European ancestry. Much of our knowledge of the epidemiology of type 1 diabetes in young people has been generated by large collaborative efforts that were centred on standardised registry data, such as the DIAMOND Project worldwide1 and the EURODIAB Study in Europe. 2 At the start of the 20th century, childhood type 1 diabetes was rare and rapidly fatal, but by the end of the century a steady increase in incidence had been reported in many parts of the world. 1 In The Lancet today, Christopher Patterson and the EURODIAB Study Group3 provide updated estimates of trends in incidence of type 1 diabetes in individuals younger than 15 years in Europe from 1989 to 2003. 15-year incidence data collected by 20 populationbased registries in 17 countries were used to estimate rates of increase in geographical regions in Europe. Model-based rates of increase were then used to predict the number of new cases throughout Europe by 2020. The prediction is that between 2005 and 2020, new cases of type 1 diabetes in European children younger than 5 years will double and that the prevalence of cases in those younger than 15 years will increase by 70%. What is the importance of these new data? The observed incidence rates confirm, and in fact exceed, the incidence predicted for 2010 by earlier projections. 4 This finding is the case for both high-risk European countries, such as Finland and Sweden, and lower-risk countries, such as Austria, Lithuania, and Poland. 3, 4 Recent data from the USA, where registry efforts have been less coordinated, suggest similar trends. For example, the multicentre SEARCH for Diabetes in Youth Study recently reported that the 2002–05 incidence of type 1 diabetes in non-Hispanic white people younger than 15 years was 27· 5 per 100 000 people per year, 5 a rate that exceeds the incidence predicted for 2010 from older data from Allegheny County. 4 Similarly, the incidence of type 1 diabetes in young people in Colorado in 2002–046 was much higher than that predicted from earlier Colorado data. 4 These findings suggest that the incidence of type 1 diabetes is increasing even faster than before, pointing towards harmful changes in the environment in which contemporary children live.