Given the success of phosphodiesterase inhibitors in both in vivo and in vitro models for prevention of oocyte maturation and pregnancy in animal models, it is reasonable that we further examine this potential non-hormonal oral contraceptive method. Given the many FDA clinical trials that need to be conducted, new contraceptive methods take decades to develop. However, since Cilostazol is an approved FDA medication with an acceptable side effect profile, we believe that it is appropriate to complete initial studies of this drug in humans using an in vivo technique validated in macaques, a model with the same timing of peri-ovulatory events as women, to ascertain its possible use as a non-hormonal oral contraceptive.