LH is a glycoprotein that plays a crucial role in folliculogenesis during the natural ovarian cycles. It has the same activity and shares receptors with hCG. However the use of LH in combination with FSH in controlled ovarian stimulation remains controversial. A practical approach concerning the usefulness of LH according to the endogenous level of LH is described herein. Specific groups of patients can benefit from ovarian stimulation with LH. New applications of LH/hCG activity are also discussed.