Many general pediatricians feel that the assessment of an infant or child who has a developmental delay and possible neurologic impairment is one of their most difficult challenges. Frequently the parents or relatives, during the course of a well-child visit, first voice concerns about the failure to attain or master one or more expected developmental milestones. Other times the pediatrician is the first to note a problem with development in one or more areas. One of the most important tasks for the pediatrician is to be able to identify the subset of patients who may have a progressive rather than a static neurologic process and to refer them promptly for further evaluation of a possible neurodegenerative disorder. In the past, the diagnosis of a childhood neurodegenerative disease was associated with a sense of hopelessness; frequently, the need for a definitive diagnosis was questioned. Breakthroughs in our understanding of the genetic and biochemical basis of many of these disorders, together with advances in enzyme replacement and gene therapy, have made antenatal diagnosis, treatments, and even cures a reality. The numerous types of central nervous system (CNS) degenerative diseases encountered in children go beyond the scope of a few pages and are covered well in the standard texts (see the excellent chapter by Johnson and Rapin in Rudolph's Pediatrics, 19th ed, 1991).