Ovarian stimulation improves the cycle fecundity rate in part by increasing the number of follicles available for fertilisation and correcting subtle, unpredictable ovulatory dysfunction. Intrauterine insemination is an established treatment for subfertility due to cervical factors, male factors, or unexplained etiology. Ovulation induction aims at the selection of a single follicle that would be able to reach the pre-ovulatory size and rupture. The ovarian sensitivity to FSH (FSH threshold) has to be identified to avoid multiple follicular development and hence, the lowest effective dose of FSH should be used in treating infertility.