Hermaphroditism is a more general term for the discrepancy between the phenotype and the genotype of sex development than sexual ambiguity, which refers mainly to external genitalia anomalies. Hermaphroditism is studied on an historical and pathogenetical perspective. Short embryological summaries are integrated. The defects of sexual differentiation due to a hormonal deficiency are first studied: androgen insensitivity, steroid 5 alpha-reductase 2 deficiency, defects of testosterone synthesis, persistent mullerian ducts syndrome. Sexual determinism deficiencies come after: Turner syndrome, XX males, pure gonadal dysgenesis, and true hermaphroditism, mixed gonadal dysgenesis, Drash and Frasier syndrome. Tumors of dysgenetic gonads followed. Mixed tumors developed in dysgenetic gonads are gonadoblastoma and dysgerminoma. Sex cord tumors are androgen insensitivity associated tumors, Leydig cells tumors and adrenal cell inclusion tumors. New perspectives open by sex reversion genes are open.