To elaborate guidelines for the use of different treatment and different protocols for ovarian stimulation. SEARCHED STRATEGY: We searched for all publications which described randomised controlled trial evaluating different ovarian stimulation protocols and different indications on PubMed, Medline and Cochrane Database. The keywords were: ovulation induction, citrate of clomiphene, gonadotropin, metformin, anti estrogens, anti aromatase, pulsatile GnRH administration, cancer, ovarian hyperstimulation, thrombosis, multiple pregnancies, and complications. Randomised controlled trials were first considered. Then was considered recent meta analysis and cohort study. We mentioned when literature was weak.