More recently numerous papers have been written on the successful paediatric applications of some well-established urinary N-acetyl-beta-D-glucosaminidase assays by several authors. Regarding these developments we tried to collect and summarize all the available literature data published in this field thus far and, in addition, to encourage and promote the wider utilization of these effective methods for the diagnosis of very different primary and secondary renal damages. Besides the chemical and biochemical background of the assays the pathological conditions and medical treatments which may lead to tubulopathy and, therefore, to a significantly elevated urinary enzyme excretion are also discussed.