This case report describes the psychosexual development of a child with true hermaphroditism who was assigned to the male sex at birth, but reassigned to the female sex at age two months. Given this child's excessive exposure to male sex hormone in utero, relative to physically normal females, one would predict a biological predisposition to behave in a masculine manner. This has occurred since two years of age. In addition, this child has had periodic episodes of gender disturbance, dysphoria, and ambivalence. In contrast, a physically normal fraternal twin sister has been conventionally feminine. A number of psychosocial factors appeared to have exacerbated the biologic predisposition to behave in a masculine manner, and thus may have been responsible for "pushing" this child into varying degrees of gender identity conflict. These included a closer father-daughter than mother-daughter relationship, parental tolerance of cross-gender behavior, and a mother who has been psychologically disturbed since the birth of her children. The heuristic value of this case will be discussed in relation to contemporary models of psychosexual development which emphasize the interaction of biological and psychosocial factors.