Advances in pediatric hematopoietic stem cell transplantation (SCT) have resulted in improved survival and prompted increased attention to the potential adverse late effects of this procedure. Survivors of SCT are thought to be at risk for neurocognitive deficits as a result of their exposure to a number of potentially neurotoxic agents. Prior studies done by our group and others have demonstrated generally stable cognitive function in the first 5 years following transplant, with little evidence of significant declines. However, there has been almost no research to date on the status of very long-term (> 5 years post-transplant) survivors. In this study, we will evaluate a large sample of long-term survivors of allogeneic SCT using measures of intelligence, academic achievement, and specific cognitive functions such as attention, working memory and processing speed. We will also obtain measures of behavioral functioning and quality of life. We will examine how this group of survivors are functioning relative to normative expectations, and in comparison to community controls without a history of serious illness, matched on age, gender, race/ethnicity, and socioeconomic status. We will also examine the relationship between cognitive function and psychosocial function and quality of life in this population.