Ambiguous genitalia in a newborn may be due to several causes. In a girl it is usually due to excess androgen production by adrenal glands (as in congenital adrenal hyperplasia, CAH), ovaries or an extraneous source. In a male child it may be due to inadequate male sex hormone (androgen) production or lack of action leading to poor development and differentiation of testes. It is possible to arrive at a diagnosis by a select battery of investigations, which include hormonal, genetic and imaging studies. The ambiguity can be corrected by surgery at appropriate age depending on the diagnosis and the assigned sex of rearing the child. Medical treatment is in addition necessary to prevent further virilisation as in CAH. It is possible to do prenatal diagnosis and treatment in some conditions such as CAH. In many situations the next child may be unaffected.