Simultaneous administration of follicle stimulating hormone, oestradiol valerate and progesterone was employed in a patient with a possible enzymatic deficiency involving low production of oestradiol. The patient became pregnant after in-vitro fertilization. This case demonstrates that this treatment is useful in women with low oestradiol production and subsequent inadequate endometrial development; it also illustrates the role of oestradiol in follicular development and questions the importance of serum oestradiol measurements in the monitoring of ovulation induction.