Specifically, chronic granulomatous disease (CGD) is an inherited disorder in which phagocytes fail to generate an oxidative burst. In 26 patients followed at the NIH tested for behavioral problems at the request of a parent or staff member, we have observed a 23% rate of mild mental retardation. However, it is not clear whether this is due to CGD per se or the recurrent infections and hospitalizations. We seek to determine the prevalence of cognitive disabilities in children with CGD and other leukocyte disorders. We seek to determine whether abnormal leukocyte functioning may be related to specific behavioral phenotypes or impaired cognitive functioning. We also seek to clarify whether impaired cognitive functioning is related to the effects of frequent and prolonged hospitalization or other variables such as severity of illness in this population.