Ovarian and pituitary-gonadal function was evaluated in 12 women who were treated with cyclophosphamide for nephrotic syndrome before or during puberty. The mean age at the start of treatment was 8.7 years; the mean total dose of cyclophosphamide was 439 mg/kg body weight; and the mean follow-up time was 12.3 years. The investigations included detailed developmental, menstrual and fertility histories; general and gynaecological examinations; basal levels and follicle-stimulating hormone and luteinizing hormone responses to gonadotropin-releasing hormone, and plasma oestradiol determinations. All patients had normal pubertal development and regular menstrual patterns. Two had borne healthy children. Although hormonal studies did not show obvious ovarian or pituitary-gonadal dysfunction, further follow-up is required to ascertain whether the patients with the most prolonged treatment undergo a premature menopause.