PROJECT SUMMARY/ABSTRACT Whether or not to surgically “correct” ambiguous genitalia in young children is an area of pediatric medicine that is highly controversial. Suboptimal outcomes such as poor cosmesis and sexual dysfunction following outdated surgical procedures have driven intense controversy in the medical community over how, or if, surgery should be used in the treatment of young children with ambiguous genitalia. To help resolve this debate, a prospective study of long-term outcomes of current surgical procedures, including complication rates associated with these procedures, is needed among individuals who receive masculinizing or feminizing surgery during early childhood. Additionally, studies of parents who decide to proceed, or not, with such surgeries for their young child are necessary to understand how these controversial decisions impact parents’ reactions to their child. Finally, better understanding of cognitive, behavioral, and social development in children born with ambiguous genitalia, including identification of novel markers for predicting gender development, is needed. The overall goal of this proposal is to assess the outcomes of modern surgical techniques with a consideration of the psychological outcomes of affected children and their parents. This information is crucial for physicians to provide guidance to parents regarding the optimal approach for the management of ambiguous genitalia in young children, including the possibility that no surgery is best. The interdisciplinary group of clinicians and researchers included in the proposed studies span the fields of psychology, statistics, pediatric endocrinology, and pediatric urology. The collective experience of our group optimizes our ability to translate findings from the proposed studies to a clinical setting in a timely manner.