In the first part of this review, we analyzed protocols for ovarian hyperstimulation with GnRH analogs and stressed both their diversity and uncertainty for mechanisms which lead to improve the outcome of IVF cycles. Apart from their beneficial effects on prevention of endogenous LH surges and premature luteinization, other adverse effects have been reported: need of higher amount of exogenous gonadotrophins, direct negative action on ovarian function and conceptus quality. They must be considered before defining a strategy for poor responders to IVF protocols using GnRH analogs. The recent trend for reducing GnRH doses must be evaluated.