Disorders of sex development are medical conditions in which the development of chromosomal, gonadal, or anatomic sex varies from normal and may be incongruent with each other. This article primarily addresses the medical conditions where infants may be born with ambiguous genitalia leading to decisions with regard to gender assignment. The approach to investigations and diagnosis in the newborn period will be stressed within an interprofessional team. Policies with regard to surgery have developed, with techniques evolving and data emerging from long-term outcome studies. Current medical and surgical management are reviewed. Finally, a developmental approach to disclosure is presented.