BACKGROUND: Little is known about the group of children on renal replacement therapy (RRT) who reach the age of 18 years and are transferred from paediatric to adult nephrology services. The aim of this study was to describe patient demographics, primary renal diseases, treatment history and determine the risk factors for mortality of these young adults who started RRT in childhood. METHODS: We included 1777 young adults who had started RRT during childhood and turned 18 between 1985 and 2004 from nine European renal registries submitting data to the ERA-EDTA Registry. The chi-square test was used to test differences between patient groups and Cox regression analysis to examine patient survival. RESULTS: Young adults who began RRT during childhood increased the total number of adult patients starting RRT by 1.5% per annum. The annual number of children on RRT turning 18, per million persons (Pmarp) reaching the age of 18 years, increased between 1985 and 2004 from 71 to 116. Over time, there was an increase in the percentage of young adults who started RRT at a very young age, a greater number of children with hypoplasia/dysplasia and cystic kidneys and more young adults who started RRT with peritoneal dialysis or pre-emptive transplantation. The unadjusted 5-year patient survival from the 18th birthday was 95.1% (95% CI 93.9-96.0). The average life expectancy was 63 years for young adults with a functioning graft and 38 years for those remaining on dialysis. CONCLUSIONS: The number Pmarp of young adults on RRT has increased over time. Their characteristics and treatment history changed. Their survival prospects are good; however, transplant recipients have an expected remaining lifetime that is at least twice as high as for young adults on dialysis.