The gonadoblastoma has been found in patients with gonadodysgenesis of a pure or mixed variety or who have male pseudo-hermaphroditism. This gonadic tumour is rarely found in true hermaphroditism. This case history would seem to be the first that has been reported in France. The patient had been followed since birth because of having an intersex state with doubtful external genital organs and male internal genital organs consisting of a testis on the left side and feminine ones consisting of an ovary on the right. The caryotype was 46 XY. The gonadoblastoma was discovered at the age of 18 following a hysterectomy with castration which had become necessary because of pyometra and a tubal abscess. The discovery was a chance one, as there had been no clinical sign suggestive of it. Since a gonadablastoma is potentially malignant this finding highlights the problem of management of the gonads in such patients when the caryotype includes the Y chromosome.