The European Dialysis and Transplant Association (E.D.T.A.) conducts a yearly survey on growth in children undergoing regular haemodialysis (HD) and renal transplantation (TR). According to the results obtained at the end of 1974 body height of 474 children starting a kidney function replacement programme was below the 3rd percentile (P.) in 40%. Growth retardation was more severe in children with congenital than with acquired kidney disorders. In boys (up to age 16) and girls (up to age 14) growth velocity (GV) was 3 years. With more frequent and longer dialyses per week GV was better in males, but not in females. In order to obtain better insight in the factors leading to growth failure on HD a more detailled survey was undertaken at the end of 1975, including data on bone age, nutrition and pubertal status.