LH plays critical roles in the control of folliculogenesis and ovarian function in humans. LH activity administration during gonadotrophin ovulation induction can enhance ovarian response and optimise treatment. More specifically, LH activity (both LH and low-dose hCG) can support the growth and stimulate the maturation of larger ovarian follicles as a result of specific granulosa cell receptors that develop after a few days of FSH priming. This action of LH is independent of FSH, and it has been shown recently that the last stages of follicular development can be supported by sole administration of LH activity in the form of low-dose hCG, without causing premature luteinization. Reproductively competent oocytes and pregnancy can be obtained with this regimen. Furthermore, LH activity is capable of reducing the development of small ovarian follicles (<10 mm) that may predispose patients to developing complications such as the ovarian hyperstimulation syndrome. Thus, better understanding of the dynamics and mechanisms that control human folliculogenesis and a more rational and selective use of LH activity administration may allow a reduction in cost and increased safety, while maintaining a high efficacy of the ovulation induction regimens used in assisted reproduction.