In gonadal dysgenesis, the presence of the Y sex chromosome appears to have a strong influence on the development of germ cell tumours. The risk of malignancy associated with other sex chromosomal abnormalities is much lower. In the present report, the clinical manifestations--including primary amenorrhoea, tall stature, infertility and poor development of the genitalia and breasts--associated with a predominantly 47, XXX karyotype are described. Malignant change of the streak ovary to an unusual gonadal stromal tumour with lipid-containing cells occurred at a late stage in her life, and this was associated with progressive virilization and production of androgenic and oestrogenic steroids. In view of the risk of malignancy as well as the abnormal endocrine effects, especially in the presence of a Y chromosome, there is a place for the prophylactic removal of these dysgenetic gonads.